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136-503: An ion source is a device that creates atomic and molecular ions . Ion sources are used to form ions for mass spectrometers , optical emission spectrometers , particle accelerators , ion implanters and ion engines . Electron ionization is widely used in mass spectrometry, particularly for organic molecules. The gas phase reaction producing electron ionization is where M is the atom or molecule being ionized, e − {\displaystyle {\ce {e^-}}}

272-404: A de Broglie wave in the manner of light . That is, under the appropriate conditions, electrons and other matter would show properties of either particles or waves. The corpuscular properties of a particle are demonstrated when it is shown to have a localized position in space along its trajectory at any given moment. The wave-like nature of light is displayed, for example, when a beam of light

408-444: A magnetic field . Electrons, due to their smaller mass and thus larger space-filling properties as matter waves , determine the size of atoms and molecules that possess any electrons at all. Thus, anions (negatively charged ions) are larger than the parent molecule or atom, as the excess electron(s) repel each other and add to the physical size of the ion, because its size is determined by its electron cloud . Cations are smaller than

544-648: A charged droplet of oil from falling as a result of gravity. This device could measure the electric charge from as few as 1–150 ions with an error margin of less than 0.3%. Comparable experiments had been done earlier by Thomson's team, using clouds of charged water droplets generated by electrolysis, and in 1911 by Abram Ioffe , who independently obtained the same result as Millikan using charged microparticles of metals, then published his results in 1913. However, oil drops were more stable than water drops because of their slower evaporation rate, and thus more suited to precise experimentation over longer periods of time. Around

680-435: A flow of inert gas, typically helium or argon . Reagents are added downstream to create ion products and study reaction rates. Flowing-afterglow mass spectrometry is used for trace gas analysis for organic compounds. Electric spark ionization is used to produce gas phase ions from a solid sample. When incorporated with a mass spectrometer the complete instrument is referred to as a spark ionization mass spectrometer or as

816-410: A fourth state of matter in which the mean free path of the particles is so long that collisions may be ignored. In 1883, not yet well-known German physicist Heinrich Hertz tried to prove that cathode rays are electrically neutral and got what he interpreted as a confident absence of deflection in electrostatic, as opposed to magnetic, field. However, as J. J. Thomson explained in 1897, Hertz placed

952-454: A free electron and a positive ion. Ions are also created by chemical interactions, such as the dissolution of a salt in liquids, or by other means, such as passing a direct current through a conducting solution, dissolving an anode via ionization . The word ion was coined from neuter present participle of Greek ἰέναι ( ienai ), meaning "to go". A cation is something that moves down ( Greek : κάτω , kato , meaning "down") and an anion

1088-494: A friction that slows the electron. This force is caused by a back-reaction of the electron's own field upon itself. Photons mediate electromagnetic interactions between particles in quantum electrodynamics . An isolated electron at a constant velocity cannot emit or absorb a real photon; doing so would violate conservation of energy and momentum . Instead, virtual photons can transfer momentum between two charged particles. This exchange of virtual photons, for example, generates

1224-415: A gas is extensively used for the detection of radiation such as alpha , beta , gamma , and X-rays . The original ionization event in these instruments results in the formation of an "ion pair"; a positive ion and a free electron, by ion impact by the radiation on the gas molecules. The ionization chamber is the simplest of these detectors, and collects all the charges created by direct ionization within

1360-400: A gas with less net electric charge is called the ionization potential , or ionization energy . The n th ionization energy of an atom is the energy required to detach its n th electron after the first n − 1 electrons have already been detached. Each successive ionization energy is markedly greater than the last. Particularly great increases occur after any given block of atomic orbitals

1496-533: A highly electronegative nonmetal, the extra electrons from the metal atoms are transferred to the electron-deficient nonmetal atoms. This reaction produces metal cations and nonmetal anions, which are attracted to each other to form a salt . Electron Electrons play an essential role in numerous physical phenomena, such as electricity , magnetism , chemistry , and thermal conductivity ; they also participate in gravitational , electromagnetic , and weak interactions . Since an electron has charge, it has

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1632-504: A metal (typically gallium ) is heated to the liquid state and provided at the end of a capillary or a needle. Then a Taylor cone is formed under the application of a strong electric field. As the cone's tip get sharper, the electric field becomes stronger, until ions are produced by field evaporation. These ion sources are particularly used in ion implantation or in focused ion beam instruments. Plasma desorption ionization mass spectrometry (PDMS), also called fission fragment ionization,

1768-483: A minus indication "Anion (−)" indicates the negative charge. With a cation it is just the opposite: it has fewer electrons than protons, giving it a net positive charge, hence the indication "Cation (+)". Since the electric charge on a proton is equal in magnitude to the charge on an electron, the net electric charge on an ion is equal to the number of protons in the ion minus the number of electrons. An anion (−) ( / ˈ æ n ˌ aɪ . ən / ANN -eye-ən , from

1904-464: A model of the electron – the Dirac equation , consistent with relativity theory, by applying relativistic and symmetry considerations to the hamiltonian formulation of the quantum mechanics of the electro-magnetic field. In order to resolve some problems within his relativistic equation, Dirac developed in 1930 a model of the vacuum as an infinite sea of particles with negative energy, later dubbed

2040-440: A molecule/atom with multiple charges is by drawing out the signs multiple times, this is often seen with transition metals. Chemists sometimes circle the sign; this is merely ornamental and does not alter the chemical meaning. All three representations of Fe , Fe , and Fe shown in the figure, are thus equivalent. Monatomic ions are sometimes also denoted with Roman numerals , particularly in spectroscopy ; for example,

2176-402: A neutral atom or molecule is called ionization . Atoms can be ionized by bombardment with radiation , but the more usual process of ionization encountered in chemistry is the transfer of electrons between atoms or molecules. This transfer is usually driven by the attaining of stable ("closed shell") electronic configurations . Atoms will gain or lose electrons depending on which action takes

2312-456: A particle with a positive charge, such as the proton, and a repulsive force on a particle with a negative charge. The strength of this force in nonrelativistic approximation is determined by Coulomb's inverse square law . When an electron is in motion, it generates a magnetic field . The Ampère–Maxwell law relates the magnetic field to the mass motion of electrons (the current ) with respect to an observer. This property of induction supplies

2448-592: A positive charge, forming the ion NH + 3 . However, this ion is unstable, because it has an incomplete valence shell around the nitrogen atom, making it a very reactive radical ion. Due to the instability of radical ions, polyatomic and molecular ions are usually formed by gaining or losing elemental ions such as H , rather than gaining or losing electrons. This allows the molecule to preserve its stable electronic configuration while acquiring an electrical charge. The energy required to detach an electron in its lowest energy state from an atom or molecule of

2584-411: A precise ionic gradient across membranes , the disruption of this gradient contributes to cell death. This is a common mechanism exploited by natural and artificial biocides , including the ion channels gramicidin and amphotericin (a fungicide ). Inorganic dissolved ions are a component of total dissolved solids , a widely known indicator of water quality . The ionizing effect of radiation on

2720-427: A radical molecular cation M, an electron e, and a neutral gas molecule G: Penning ionization occurs when the target molecule has an ionization potential lower than the internal energy of the excited-state atom or molecule. Associative Penning ionization can proceed via Surface Penning ionization (also known as Auger deexcitation) refers to the interaction of the excited-state gas with a bulk surface S, resulting in

2856-414: A sample deposited on a porous silicon surface. A laser vaporization cluster source produces ions using a combination of laser desorption ionization and supersonic expansion. The Smalley source (or Smalley cluster source ) was developed by Richard Smalley at Rice University in the 1980s and was central to the discovery of fullerenes in 1985. Ion An ion ( / ˈ aɪ . ɒ n , - ən / )

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2992-406: A separation (together with an appropriate gas-flow scheme) may help reduce the negative effect, that particles released from a processed substrate may have on the plasma chemistry of the gas phase . The ECR ion source makes use of the electron cyclotron resonance to ionize a plasma. Microwaves are injected into a volume at the frequency corresponding to the electron cyclotron resonance, defined by

3128-604: A single electron. This prohibition against more than one electron occupying the same quantum energy state became known as the Pauli exclusion principle . The physical mechanism to explain the fourth parameter, which had two distinct possible values, was provided by the Dutch physicists Samuel Goudsmit and George Uhlenbeck . In 1925, they suggested that an electron, in addition to the angular momentum of its orbit, possesses an intrinsic angular momentum and magnetic dipole moment . This

3264-482: A solution that determined the location of an electron over time, this wave equation also could be used to predict the probability of finding an electron near a position, especially a position near where the electron was bound in space, for which the electron wave equations did not change in time. This approach led to a second formulation of quantum mechanics (the first by Heisenberg in 1925), and solutions of Schrödinger's equation, like Heisenberg's, provided derivations of

3400-458: A spark source mass spectrometer (SSMS). A closed drift ion source uses a radial magnetic field in an annular cavity in order to confine electrons for ionizing a gas. They are used for ion implantation and for space propulsion ( Hall-effect thrusters ). Photoionization is the ionization process in which an ion is formed from the interaction of a photon with an atom or molecule. In multi-photon ionization (MPI), several photons of energy below

3536-402: A spray of solvent is heated to relatively high temperatures (above 400 degrees Celsius) and sprayed with high flow rates of nitrogen for desolvation. The resulting aerosol is subjected to UV radiation to create ions. Atmospheric-pressure laser ionization uses UV laser light sources to ionize the analyte via MPI. Field desorption refers to an ion source in which a high-potential electric field

3672-414: A stable configuration. This property is known as electropositivity . Non-metals, on the other hand, are characterized by having an electron configuration just a few electrons short of a stable configuration. As such, they have the tendency to gain more electrons in order to achieve a stable configuration. This tendency is known as electronegativity . When a highly electropositive metal is combined with

3808-437: A surplus of the charge carrier, and which situation was a deficit. Between 1838 and 1851, British natural philosopher Richard Laming developed the idea that an atom is composed of a core of matter surrounded by subatomic particles that had unit electric charges . Beginning in 1846, German physicist Wilhelm Eduard Weber theorized that electricity was composed of positively and negatively charged fluids, and their interaction

3944-514: A surrounding electric field ; if that electron is moving relative to an observer, the observer will observe it to generate a magnetic field . Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law . Electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by

4080-401: A −2 charge is known as a dianion and an ion with a +2 charge is known as a dication . A zwitterion is a neutral molecule with positive and negative charges at different locations within that molecule. Cations and anions are measured by their ionic radius and they differ in relative size: "Cations are small, most of them less than 10 m (10 cm) in radius. But most anions are large, as is

4216-407: Is a challenging problem of modern theoretical physics. The admission of the hypothesis of a finite radius of the electron is incompatible to the premises of the theory of relativity. On the other hand, a point-like electron (zero radius) generates serious mathematical difficulties due to the self-energy of the electron tending to infinity. Observation of a single electron in a Penning trap suggests

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4352-489: Is a combination of conventional SALDI with ambient mass spectrometry incorporating the DART ion source - has also been demonstrated. Surface-enhanced laser desorption/ionization (SELDI) is a variant of MALDI that is used for the analysis of protein mixtures that uses a target modified to achieve biochemical affinity with the analyte compound. Desorption ionization on silicon (DIOS) refers to laser desorption/ionization of

4488-467: Is a combination of the words electr ic and i on . The suffix - on which is now used to designate other subatomic particles, such as a proton or neutron, is in turn derived from electron. While studying electrical conductivity in rarefied gases in 1859, the German physicist Julius Plücker observed the radiation emitted from the cathode caused phosphorescent light to appear on the tube wall near

4624-412: Is a mass spectrometry technique in which ionization of material in a solid sample is accomplished by bombarding it with ionic or neutral atoms formed as a result of the nuclear fission of a suitable nuclide , typically the californium isotope Cf. Matrix-assisted laser desorption/ionization (MALDI) is a soft ionization technique. The sample is mixed with a matrix material. Upon receiving a laser pulse,

4760-416: Is a negatively charged ion with more electrons than protons. (e.g. Cl (chloride ion) and OH (hydroxide ion)). Opposite electric charges are pulled towards one another by electrostatic force , so cations and anions attract each other and readily form ionic compounds . If only a + or - is present, it indicates a +1 or -1 charge. To indicate a more severe charge, the number of additional or missing atoms

4896-496: Is actually smaller than its true value, and the charge decreases with increasing distance from the electron. This polarization was confirmed experimentally in 1997 using the Japanese TRISTAN particle accelerator. Virtual particles cause a comparable shielding effect for the mass of the electron. The interaction with virtual particles also explains the small (about 0.1%) deviation of the intrinsic magnetic moment of

5032-484: Is an atom or molecule with a net electrical charge . The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton , which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons (e.g. K (potassium ion)) while an anion

5168-592: Is analogous to the rotation of the Earth on its axis as it orbits the Sun. The intrinsic angular momentum became known as spin , and explained the previously mysterious splitting of spectral lines observed with a high-resolution spectrograph ; this phenomenon is known as fine structure splitting. In his 1924 dissertation Recherches sur la théorie des quanta (Research on Quantum Theory), French physicist Louis de Broglie hypothesized that all matter can be represented as

5304-453: Is applied to an emitter with a sharp surface, such as a razor blade, or more commonly, a filament from which tiny "whiskers" have formed. This results in a very high electric field which can result in ionization of gaseous molecules of the analyte. Mass spectra produced by FI have little or no fragmentation. They are dominated by molecular radical cations M and less often, protonated molecules [M + H] Particle bombardment with atoms

5440-479: Is approximately 9.109 × 10  kg , or 5.489 × 10   Da . Due to mass–energy equivalence , this corresponds to a rest energy of 0.511 MeV (8.19 × 10  J) . The ratio between the mass of a proton and that of an electron is about 1836. Astronomical measurements show that the proton-to-electron mass ratio has held the same value, as is predicted by the Standard Model, for at least half

5576-493: Is bombarded under vacuum with a high energy (4000 to 10,000 electron volts ) beam of atoms. The atoms are typically from an inert gas such as argon or xenon . Common matrices include glycerol , thioglycerol , 3-nitrobenzyl alcohol (3-NBA), 18-crown-6 ether, 2-nitrophenyloctyl ether , sulfolane , diethanolamine , and triethanolamine . This technique is similar to secondary ion mass spectrometry and plasma desorption mass spectrometry. Secondary ion mass spectrometry (SIMS)

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5712-466: Is called fast atom bombardment (FAB) and bombardment with atomic or molecular ions is called secondary ion mass spectrometry (SIMS). Fission fragment ionization uses ionic or neutral atoms formed as a result of the nuclear fission of a suitable nuclide , for example the Californium isotope Cf. In FAB the analytes is mixed with a non-volatile chemical protection environment called a matrix and

5848-429: Is exhausted of electrons. For this reason, ions tend to form in ways that leave them with full orbital blocks. For example, sodium has one valence electron in its outermost shell, so in ionized form it is commonly found with one lost electron, as Na . On the other side of the periodic table, chlorine has seven valence electrons, so in ionized form it is commonly found with one gained electron, as Cl . Caesium has

5984-455: Is in existence, the Coulomb force from the ambient electric field surrounding an electron causes a created positron to be attracted to the original electron, while a created electron experiences a repulsion. This causes what is called vacuum polarization . In effect, the vacuum behaves like a medium having a dielectric permittivity more than unity . Thus the effective charge of an electron

6120-615: Is in the breakdown of adenosine triphosphate ( ATP ), which provides the energy for many reactions in biological systems. Ions can be non-chemically prepared using various ion sources , usually involving high voltage or temperature. These are used in a multitude of devices such as mass spectrometers , optical emission spectrometers , particle accelerators , ion implanters , and ion engines . As reactive charged particles, they are also used in air purification by disrupting microbes, and in household items such as smoke detectors . As signalling and metabolism in organisms are controlled by

6256-570: Is one of humanity's earliest recorded experiences with electricity . In his 1600 treatise De Magnete , the English scientist William Gilbert coined the Neo-Latin term electrica , to refer to those substances with property similar to that of amber which attract small objects after being rubbed. Both electric and electricity are derived from the Latin ēlectrum (also the root of

6392-607: Is one short of the stable, filled shell with 8 electrons. Thus, a chlorine atom tends to gain an extra electron and attain a stable 8- electron configuration , becoming a chloride anion in the process: This driving force is what causes sodium and chlorine to undergo a chemical reaction, wherein the "extra" electron is transferred from sodium to chlorine, forming sodium cations and chloride anions. Being oppositely charged, these cations and anions form ionic bonds and combine to form sodium chloride , NaCl, more commonly known as table salt. Polyatomic and molecular ions are often formed by

6528-407: Is passed through parallel slits thereby creating interference patterns. In 1927, George Paget Thomson and Alexander Reid discovered the interference effect was produced when a beam of electrons was passed through thin celluloid foils and later metal films, and by American physicists Clinton Davisson and Lester Germer by the reflection of electrons from a crystal of nickel . Alexander Reid, who

6664-451: Is possible to mix the notations for the individual metal centre with a polyatomic complex, as shown by the uranyl ion example. If an ion contains unpaired electrons , it is called a radical ion. Just like uncharged radicals, radical ions are very reactive. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions . Molecular ions that contain at least one carbon to hydrogen bond are called organic ions . If

6800-467: Is shared by the electron beam ion trap . Electron capture ionization (ECI) is the ionization of a gas phase atom or molecule by attachment of an electron to create an ion of the form A. The reaction is where the M over the arrow denotes that to conserve energy and momentum a third body is required (the molecularity of the reaction is three). Electron capture can be used in conjunction with chemical ionization . An electron capture detector

6936-418: Is something that moves up ( Greek : ἄνω , ano , meaning "up"). They are so called because ions move toward the electrode of opposite charge. This term was introduced (after a suggestion by the English polymath William Whewell ) by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday did not know

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7072-415: Is supplied, as seen in O 2 (negative charge, peroxide ) and He (positive charge, alpha particle ). Ions consisting of only a single atom are termed atomic or monatomic ions , while two or more atoms form molecular ions or polyatomic ions . In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of

7208-407: Is the electron, and M + ∙ {\displaystyle {\ce {M^{+\bullet }}}} is the resulting ion. The electrons may be created by an arc discharge between a cathode and an anode . An electron beam ion source (EBIS) is used in atomic physics to produce highly charged ions by bombarding atoms with a powerful electron beam . Its principle of operation

7344-482: Is the excited state species (indicated by the superscripted asterisk), and M is the species that is ionized by the loss of an electron to form the radical cation (indicated by the superscripted "plus-dot"). Associative ionization is a gas phase reaction in which two atoms or molecules interact to form a single product ion. One or both of the interacting species may have excess internal energy . For example, where species A with excess internal energy (indicated by

7480-608: Is used in ionization smoke detectors and ion mobility spectrometers . These ion sources use a plasma source or electric discharge to create ions. Ions can be created in an inductively coupled plasma, which is a plasma source in which the energy is supplied by electrical currents which are produced by electromagnetic induction , that is, by time-varying magnetic fields . Microwave induced plasma ion sources are capable of exciting electrodeless gas discharges to create ions for trace element mass spectrometry. A microwave plasma has high frequency electromagnetic radiation in

7616-411: Is used in some gas chromatography systems. Chemical ionization (CI) is a lower energy process than electron ionization because it involves ion/molecule reactions rather than electron removal. The lower energy yields less fragmentation , and usually a simpler spectrum . A typical CI spectrum has an easily identifiable molecular ion. In a CI experiment, ions are produced through the collision of

7752-428: Is used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. The mass/charge ratios of these secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface to a depth of 1 to 2 nm. In a liquid metal ion source (LMIS),

7888-432: Is written in superscript immediately after the chemical structure for the molecule/atom. The net charge is written with the magnitude before the sign; that is, a doubly charged cation is indicated as 2+ instead of +2 . However, the magnitude of the charge is omitted for singly charged molecules/atoms; for example, the sodium cation is indicated as Na and not Na . An alternative (and acceptable) way of showing

8024-556: The Fe (positively doubly charged) example seen above is referred to as Fe(III) , Fe or Fe III (Fe I for a neutral Fe atom, Fe II for a singly ionized Fe ion). The Roman numeral designates the formal oxidation state of an element, whereas the superscripted Indo-Arabic numerals denote the net charge. The two notations are, therefore, exchangeable for monatomic ions, but the Roman numerals cannot be applied to polyatomic ions. However, it

8160-461: The Dirac sea . This led him to predict the existence of a positron, the antimatter counterpart of the electron. This particle was discovered in 1932 by Carl Anderson , who proposed calling standard electrons negatrons and using electron as a generic term to describe both the positively and negatively charged variants. In 1947, Willis Lamb , working in collaboration with graduate student Robert Retherford , found that certain quantum states of

8296-480: The GHz range. It is capable of exciting electrodeless gas discharges . If applied in surface-wave-sustained mode , they are especially well suited to generate large-area plasmas of high plasma density. If they are both in surface-wave and resonator mode , they can exhibit a high degree of spatial localization. This allows to spatially separate the location of plasma generations from the location of surface processing. Such

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8432-458: The Lamb shift observed in spectral lines . The Compton Wavelength shows that near elementary particles such as the electron, the uncertainty of the energy allows for the creation of virtual particles near the electron. This wavelength explains the "static" of virtual particles around elementary particles at a close distance. An electron generates an electric field that exerts an attractive force on

8568-476: The Standard Model of particle physics. Individual electrons can now be easily confined in ultra small ( L = 20 nm , W = 20 nm ) CMOS transistors operated at cryogenic temperature over a range of −269 °C (4  K ) to about −258 °C (15  K ). The electron wavefunction spreads in a semiconductor lattice and negligibly interacts with the valence band electrons, so it can be treated in

8704-416: The absolute value of this function is squared , it gives the probability that a particle will be observed near a location—a probability density . Electrons are identical particles because they cannot be distinguished from each other by their intrinsic physical properties. In quantum mechanics, this means that a pair of interacting electrons must be able to swap positions without an observable change to

8840-414: The age of the universe . Electrons have an electric charge of −1.602 176 634 × 10 coulombs , which is used as a standard unit of charge for subatomic particles, and is also called the elementary charge . Within the limits of experimental accuracy, the electron charge is identical to the charge of a proton, but with the opposite sign. The electron is commonly symbolized by e , and

8976-726: The alloy of the same name ), which came from the Greek word for amber, ἤλεκτρον ( ēlektron ). In the early 1700s, French chemist Charles François du Fay found that if a charged gold-leaf is repulsed by glass rubbed with silk, then the same charged gold-leaf is attracted by amber rubbed with wool. From this and other results of similar types of experiments, du Fay concluded that electricity consists of two electrical fluids , vitreous fluid from glass rubbed with silk and resinous fluid from amber rubbed with wool. These two fluids can neutralize each other when combined. American scientist Ebenezer Kinnersley later also independently reached

9112-405: The double-slit experiment . The wave-like nature of the electron allows it to pass through two parallel slits simultaneously, rather than just one slit as would be the case for a classical particle. In quantum mechanics, the wave-like property of one particle can be described mathematically as a complex -valued function, the wave function , commonly denoted by the Greek letter psi ( ψ ). When

9248-462: The e / m ratio but did not take the step of interpreting their results as showing a new particle, while J. J. Thomson would subsequently in 1899 give estimates for the electron charge and mass as well: e  ~  6.8 × 10   esu and m  ~  3 × 10  g The name "electron" was adopted for these particles by the scientific community, mainly due to the advocation by G. F. FitzGerald , J. Larmor , and H. A. Lorentz . The term

9384-414: The muon and the tau , which are identical to the electron in charge, spin and interactions , but are more massive. Leptons differ from the other basic constituent of matter, the quarks , by their lack of strong interaction . All members of the lepton group are fermions because they all have half-odd integer spin; the electron has spin ⁠ 1 / 2 ⁠ . The invariant mass of an electron

9520-459: The spectral lines of the hydrogen atom. However, Bohr's model failed to account for the relative intensities of the spectral lines and it was unsuccessful in explaining the spectra of more complex atoms. Chemical bonds between atoms were explained by Gilbert Newton Lewis , who in 1916 proposed that a covalent bond between two atoms is maintained by a pair of electrons shared between them. Later, in 1927, Walter Heitler and Fritz London gave

9656-399: The spinon , the orbiton and the holon (or chargon). The electron can always be theoretically considered as a bound state of the three, with the spinon carrying the spin of the electron, the orbiton carrying the orbital degree of freedom and the chargon carrying the charge, but in certain conditions they can behave as independent quasiparticles . The issue of the radius of the electron

9792-400: The striking voltage , the gas forms a plasma. A duoplasmatron is a type of glow discharge ion source that consists of a hot cathode or cold cathode that produces a plasma that is used to ionize a gas. THey can produce positive or negative ions. They are used for secondary ion mass spectrometry, ion beam etching, and high-energy physics. In a flowing plasma afterglow, ions are formed in

9928-599: The 1870s, the English chemist and physicist Sir William Crookes developed the first cathode-ray tube to have a high vacuum inside. He then showed in 1874 that the cathode rays can turn a small paddle wheel when placed in their path. Therefore, he concluded that the rays carried momentum. Furthermore, by applying a magnetic field, he was able to deflect the rays, thereby demonstrating that the beam behaved as though it were negatively charged. In 1879, he proposed that these properties could be explained by regarding cathode rays as composed of negatively charged gaseous molecules in

10064-477: The Coulomb force. Energy emission can occur when a moving electron is deflected by a charged particle, such as a proton. The deceleration of the electron results in the emission of Bremsstrahlung radiation. An inelastic collision between a photon (light) and a solitary (free) electron is called Compton scattering . This collision results in a transfer of momentum and energy between the particles, which modifies

10200-541: The Greek word ἄνω ( ánō ), meaning "up" ) is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively charged and protons are positively charged). A cation (+) ( / ˈ k æ t ˌ aɪ . ən / KAT -eye-ən , from the Greek word κάτω ( kátō ), meaning "down" ) is an ion with fewer electrons than protons, giving it a positive charge. There are additional names used for ions with multiple charges. For example, an ion with

10336-503: The analyte are formed by reactions with this plasma. For example, protonation occurs by Charge-exchange ionization (also known as charge-transfer ionization) is a gas phase reaction between an ion and an atom or molecule in which the charge of the ion is transferred to the neutral species. Chemi-ionization is the formation of an ion through the reaction of a gas phase atom or molecule with an atom or molecule in an excited state . Chemi-ionization can be represented by where G

10472-426: The analyte with ions of a reagent gas in the ion source. Some common reagent gases include: methane , ammonia , and isobutane . Inside the ion source, the reagent gas is present in large excess compared to the analyte. Electrons entering the source will preferentially ionize the reagent gas. The resultant collisions with other reagent gas molecules will create an ionization plasma . Positive and negative ions of

10608-406: The asterisk) interacts with B to form the ion AB. Penning ionization is a form of chemi-ionization involving reactions between neutral atoms or molecules. The process is named after the Dutch physicist Frans Michel Penning who first reported it in 1927. Penning ionization involves a reaction between a gas-phase excited-state atom or molecule G and a target molecule M resulting in the formation of

10744-420: The atmosphere. The antiparticle of the electron is called the positron ; it is identical to the electron, except that it carries electrical charge of the opposite sign. When an electron collides with a positron , both particles can be annihilated , producing gamma ray photons . The ancient Greeks noticed that amber attracted small objects when rubbed with fur. Along with lightning , this phenomenon

10880-480: The beginning of the twentieth century, it was found that under certain conditions a fast-moving charged particle caused a condensation of supersaturated water vapor along its path. In 1911, Charles Wilson used this principle to devise his cloud chamber so he could photograph the tracks of charged particles, such as fast-moving electrons. By 1914, experiments by physicists Ernest Rutherford , Henry Moseley , James Franck and Gustav Hertz had largely established

11016-402: The cathode; and the region of the phosphorescent light could be moved by application of a magnetic field. In 1869, Plücker's student Johann Wilhelm Hittorf found that a solid body placed in between the cathode and the phosphorescence would cast a shadow upon the phosphorescent region of the tube. Hittorf inferred that there are straight rays emitted from the cathode and that the phosphorescence

11152-553: The charge carriers were much heavier hydrogen or nitrogen atoms. Schuster's estimates would subsequently turn out to be largely correct. In 1892 Hendrik Lorentz suggested that the mass of these particles (electrons) could be a consequence of their electric charge. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became

11288-519: The charge in an organic ion is formally centred on a carbon, it is termed a carbocation (if positively charged) or carbanion (if negatively charged). Monatomic ions are formed by the gain or loss of electrons to the valence shell (the outer-most electron shell) in an atom. The inner shells of an atom are filled with electrons that are tightly bound to the positively charged atomic nucleus , and so do not participate in this kind of chemical interaction. The process of gaining or losing electrons from

11424-588: The concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge "electron" in 1891, and J. J. Thomson and his team of British physicists identified it as a particle in 1897 during the cathode-ray tube experiment . Electrons participate in nuclear reactions , such as nucleosynthesis in stars , where they are known as beta particles . Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance, when cosmic rays enter

11560-409: The corresponding parent atom or molecule due to the smaller size of the electron cloud. One particular cation (that of hydrogen) contains no electrons, and thus consists of a single proton – much smaller than the parent hydrogen atom. Anion (−) and cation (+) indicate the net electric charge on an ion. An ion that has more electrons than protons, giving it a net negative charge, is named an anion, and

11696-430: The deflecting electrodes in a highly-conductive area of the tube, resulting in a strong screening effect close to their surface. The German-born British physicist Arthur Schuster expanded upon Crookes's experiments by placing metal plates parallel to the cathode rays and applying an electric potential between the plates. The field deflected the rays toward the positively charged plate, providing further evidence that

11832-427: The effects of quantum mechanics ; in reality, the so-called classical electron radius has little to do with the true fundamental structure of the electron. There are elementary particles that spontaneously decay into less massive particles. An example is the muon , with a mean lifetime of 2.2 × 10  seconds, which decays into an electron, a muon neutrino and an electron antineutrino . The electron, on

11968-454: The electron from the Bohr magneton (the anomalous magnetic moment ). The extraordinarily precise agreement of this predicted difference with the experimentally determined value is viewed as one of the great achievements of quantum electrodynamics . The apparent paradox in classical physics of a point particle electron having intrinsic angular momentum and magnetic moment can be explained by

12104-560: The electron has an intrinsic magnetic moment along its spin axis. It is approximately equal to one Bohr magneton , which is a physical constant that is equal to 9.274 010 0657 (29) × 10  J⋅T . The orientation of the spin with respect to the momentum of the electron defines the property of elementary particles known as helicity . The electron has no known substructure . Nevertheless, in condensed matter physics , spin–charge separation can occur in some materials. In such cases, electrons 'split' into three independent particles,

12240-456: The energy states of an electron in a hydrogen atom that were equivalent to those that had been derived first by Bohr in 1913, and that were known to reproduce the hydrogen spectrum. Once spin and the interaction between multiple electrons were describable, quantum mechanics made it possible to predict the configuration of electrons in atoms with atomic numbers greater than hydrogen. In 1928, building on Wolfgang Pauli's work, Paul Dirac produced

12376-448: The first high-energy particle collider was ADONE , which began operations in 1968. This device accelerated electrons and positrons in opposite directions, effectively doubling the energy of their collision when compared to striking a static target with an electron. The Large Electron–Positron Collider (LEP) at CERN , which was operational from 1989 to 2000, achieved collision energies of 209 GeV and made important measurements for

12512-406: The formation of virtual photons in the electric field generated by the electron. These photons can heuristically be thought of as causing the electron to shift about in a jittery fashion (known as zitterbewegung ), which results in a net circular motion with precession . This motion produces both the spin and the magnetic moment of the electron. In atoms, this creation of virtual photons explains

12648-568: The full explanation of the electron-pair formation and chemical bonding in terms of quantum mechanics . In 1919, the American chemist Irving Langmuir elaborated on the Lewis's static model of the atom and suggested that all electrons were distributed in successive "concentric (nearly) spherical shells, all of equal thickness". In turn, he divided the shells into a number of cells each of which contained one pair of electrons. With this model Langmuir

12784-454: The gaining or losing of elemental ions such as a proton, H , in neutral molecules. For example, when ammonia , NH 3 , accepts a proton, H —a process called protonation —it forms the ammonium ion, NH + 4 . Ammonia and ammonium have the same number of electrons in essentially the same electronic configuration , but ammonium has an extra proton that gives it a net positive charge. Ammonia can also lose an electron to gain

12920-435: The gas through the application of an electric field. The Geiger–Müller tube and the proportional counter both use a phenomenon known as a Townsend avalanche to multiply the effect of the original ionizing event by means of a cascade effect whereby the free electrons are given sufficient energy by the electric field to release further electrons by ion impact. When writing the chemical formula for an ion, its net charge

13056-421: The hydrogen atom, which should have the same energy, were shifted in relation to each other; the difference came to be called the Lamb shift . About the same time, Polykarp Kusch , working with Henry M. Foley , discovered the magnetic moment of the electron is slightly larger than predicted by Dirac's theory. This small difference was later called anomalous magnetic dipole moment of the electron. This difference

13192-500: The ionization threshold may actually combine their energies to ionize an atom. Resonance-enhanced multiphoton ionization (REMPI) is a form of MPI in which one or more of the photons accesses a bound-bound transition that is resonant in the atom or molecule being ionized. Atmospheric pressure photoionization (APPI) uses a source of photons, usually a vacuum UV (VUV) lamp, to ionize the analyte with single photon ionization process. Analogous to other atmospheric pressure ion sources,

13328-417: The least energy. For example, a sodium atom, Na, has a single electron in its valence shell, surrounding 2 stable, filled inner shells of 2 and 8 electrons. Since these filled shells are very stable, a sodium atom tends to lose its extra electron and attain this stable configuration, becoming a sodium cation in the process On the other hand, a chlorine atom, Cl, has 7 electrons in its valence shell, which

13464-641: The liquid or solid state when salts interact with solvents (for example, water) to produce solvated ions , which are more stable, for reasons involving a combination of energy and entropy changes as the ions move away from each other to interact with the liquid. These stabilized species are more commonly found in the environment at low temperatures. A common example is the ions present in seawater, which are derived from dissolved salts. As charged objects, ions are attracted to opposite electric charges (positive to negative, and vice versa) and repelled by like charges. When they move, their trajectories can be deflected by

13600-409: The lowest measured ionization energy of all the elements and helium has the greatest. In general, the ionization energy of metals is much lower than the ionization energy of nonmetals , which is why, in general, metals will lose electrons to form positively charged ions and nonmetals will gain electrons to form negatively charged ions. Ionic bonding is a kind of chemical bonding that arises from

13736-409: The luminescence of the Sun to the existence of the Earth's ionosphere . Atoms in their ionic state may have a different color from neutral atoms, and thus light absorption by metal ions gives the color of gemstones . In both inorganic and organic chemistry (including biochemistry), the interaction of water and ions is often relevant for understanding properties of systems; an example of their importance

13872-489: The magnetic field and the electron velocity. This centripetal force causes the electron to follow a helical trajectory through the field at a radius called the gyroradius . The acceleration from this curving motion induces the electron to radiate energy in the form of synchrotron radiation. The energy emission in turn causes a recoil of the electron, known as the Abraham–Lorentz–Dirac Force , which creates

14008-405: The magnetic field applied to a region inside the volume. The volume contains a low pressure gas. Ions can be created in an electric glow discharge. A glow discharge is a plasma formed by the passage of electric current through a low-pressure gas. It is created by applying a voltage between two metal electrodes in an evacuated chamber containing gas. When the voltage exceeds a certain value, called

14144-462: The magnetic field that drives an electric motor . The electromagnetic field of an arbitrary moving charged particle is expressed by the Liénard–Wiechert potentials , which are valid even when the particle's speed is close to that of light ( relativistic ). When an electron is moving through a magnetic field, it is subject to the Lorentz force that acts perpendicularly to the plane defined by

14280-706: The matrix absorbs the laser energy and it is thought that primarily the matrix is desorbed and ionized (by addition of a proton) by this event. The analyte molecules are also desorbed. The matrix is then thought to transfer proton to the analyte molecules (e.g., protein molecules), thus charging the analyte. Surface-assisted laser desorption/ionization (SALDI) is a soft laser desorption technique used for analyzing biomolecules by mass spectrometry . In its first embodiment, it used graphite matrix. At present, laser desorption/ionization methods using other inorganic matrices, such as nanomaterials , are often regarded as SALDI variants. A related method named "ambient SALDI" - which

14416-479: The most common Earth anion, oxygen . From this fact it is apparent that most of the space of a crystal is occupied by the anion and that the cations fit into the spaces between them." The terms anion and cation (for ions that respectively travel to the anode and cathode during electrolysis) were introduced by Michael Faraday in 1834 following his consultation with William Whewell . Ions are ubiquitous in nature and are responsible for diverse phenomena from

14552-454: The mutual attraction of oppositely charged ions. Ions of like charge repel each other, and ions of opposite charge attract each other. Therefore, ions do not usually exist on their own, but will bind with ions of opposite charge to form a crystal lattice . The resulting compound is called an ionic compound , and is said to be held together by ionic bonding . In ionic compounds there arise characteristic distances between ion neighbours from which

14688-451: The nature of these species, but he knew that since metals dissolved into and entered a solution at one electrode and new metal came forth from a solution at the other electrode; that some kind of substance has moved through the solution in a current. This conveys matter from one place to the other. In correspondence with Faraday, Whewell also coined the words anode and cathode , as well as anion and cation as ions that are attracted to

14824-426: The negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. Thomson measured m / e for cathode ray "corpuscles", and made good estimates of the charge e , leading to value for the mass m , finding a value 1400 times less massive than the least massive ion known: hydrogen. In the same year Emil Wiechert and Walter Kaufmann also calculated

14960-430: The other hand, is thought to be stable on theoretical grounds: the electron is the least massive particle with non-zero electric charge, so its decay would violate charge conservation . The experimental lower bound for the electron's mean lifetime is 6.6 × 10 years, at a 90% confidence level . As with all particles, electrons can act as waves. This is called the wave–particle duality and can be demonstrated using

15096-551: The photon, have symmetric wave functions instead. In the case of antisymmetry, solutions of the wave equation for interacting electrons result in a zero probability that each pair will occupy the same location or state. This is responsible for the Pauli exclusion principle , which precludes any two electrons from occupying the same quantum state. This principle explains many of the properties of electrons. For example, it causes groups of bound electrons to occupy different orbitals in an atom, rather than all overlapping each other in

15232-456: The positive protons within atomic nuclei and the negative electrons without allows the composition of the two known as atoms . Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding . In 1838, British natural philosopher Richard Laming first hypothesized

15368-452: The positron is symbolized by e . The electron has an intrinsic angular momentum or spin of ⁠ ħ / 2 ⁠ . This property is usually stated by referring to the electron as a spin-1/2 particle. For such particles the spin magnitude is ⁠ ħ / 2 ⁠ , while the result of the measurement of a projection of the spin on any axis can only be ± ⁠ ħ / 2 ⁠ . In addition to spin,

15504-403: The rays carried negative charge. By measuring the amount of deflection for a given electric and magnetic field , in 1890 Schuster was able to estimate the charge-to-mass ratio of the ray components. However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. This is because it was assumed that

15640-405: The release of an electron according to Ion-attachment ionization is similar to chemical ionization in which a cation is attached to the analyte molecule in a reactive collision: Where M is the analyte molecule, X is the cation and A is a non-reacting collision partner. In a radioactive ion source, a small piece of radioactive material, for instance Ni or Am , is used to ionize a gas. This

15776-664: The respective electrodes. Svante Arrhenius put forth, in his 1884 dissertation, the explanation of the fact that solid crystalline salts dissociate into paired charged particles when dissolved, for which he would win the 1903 Nobel Prize in Chemistry. Arrhenius' explanation was that in forming a solution, the salt dissociates into Faraday's ions, he proposed that ions formed even in the absence of an electric current. Ions in their gas-like state are highly reactive and will rapidly interact with ions of opposite charge to give neutral molecules or ionic salts. Ions are also produced in

15912-455: The same conclusion. A decade later Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess (+) or deficit (−). He gave them the modern charge nomenclature of positive and negative respectively. Franklin thought of the charge carrier as being positive, but he did not correctly identify which situation was

16048-423: The same orbit. In a simplified picture, which often tends to give the wrong idea but may serve to illustrate some aspects, every photon spends some time as a combination of a virtual electron plus its antiparticle, the virtual positron, which rapidly annihilate each other shortly thereafter. The combination of the energy variation needed to create these particles, and the time during which they exist, fall under

16184-489: The single particle formalism, by replacing its mass with the effective mass tensor . In the Standard Model of particle physics, electrons belong to the group of subatomic particles called leptons , which are believed to be fundamental or elementary particles . Electrons have the lowest mass of any charged lepton (or electrically charged particle of any type) and belong to the first generation of fundamental particles. The second and third generation contain charged leptons,

16320-434: The spatial extension and the ionic radius of individual ions may be derived. The most common type of ionic bonding is seen in compounds of metals and nonmetals (except noble gases , which rarely form chemical compounds). Metals are characterized by having a small number of electrons in excess of a stable, closed-shell electronic configuration . As such, they have the tendency to lose these extra electrons in order to attain

16456-435: The state of the system. The wave function of fermions, including electrons, is antisymmetric, meaning that it changes sign when two electrons are swapped; that is, ψ ( r 1 , r 2 ) = − ψ ( r 2 , r 1 ) , where the variables r 1 and r 2 correspond to the first and second electrons, respectively. Since the absolute value is not changed by a sign swap, this corresponds to equal probabilities. Bosons , such as

16592-484: The structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. In 1913, Danish physicist Niels Bohr postulated that electrons resided in quantized energy states, with their energies determined by the angular momentum of the electron's orbit about the nucleus. The electrons could move between those states, or orbits, by the emission or absorption of photons of specific frequencies. By means of these quantized orbits, he accurately explained

16728-504: The subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta , on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for cathode rays. This evidence strengthened

16864-423: The term electrolion in 1881. Ten years later, he switched to electron to describe these elementary charges, writing in 1894: "... an estimate was made of the actual amount of this most remarkable fundamental unit of electricity, for which I have since ventured to suggest the name electron ". A 1906 proposal to change to electrion failed because Hendrik Lorentz preferred to keep electron . The word electron

17000-522: The threshold of detectability expressed by the Heisenberg uncertainty relation , Δ E  · Δ t  ≥  ħ . In effect, the energy needed to create these virtual particles, Δ E , can be "borrowed" from the vacuum for a period of time, Δ t , so that their product is no more than the reduced Planck constant , ħ ≈ 6.6 × 10  eV·s . Thus, for a virtual electron, Δ t is at most 1.3 × 10  s . While an electron–positron virtual pair

17136-426: The upper limit of the particle's radius to be 10  meters. The upper bound of the electron radius of 10  meters can be derived using the uncertainty relation in energy. There is also a physical constant called the " classical electron radius ", with the much larger value of 2.8179 × 10  m , greater than the radius of the proton. However, the terminology comes from a simplistic calculation that ignores

17272-624: The use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications, such as tribology or frictional charging, electrolysis, electrochemistry, battery technologies, electronics , welding , cathode-ray tubes , photoelectricity, photovoltaic solar panels, electron microscopes , radiation therapy , lasers , gaseous ionization detectors , and particle accelerators . Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics . The Coulomb force interaction between

17408-487: The view that electrons existed as components of atoms. In 1897, the British physicist J. J. Thomson , with his colleagues John S. Townsend and H. A. Wilson , performed experiments indicating that cathode rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. By 1899 he showed that their charge-to-mass ratio, e / m , was independent of cathode material. He further showed that

17544-473: The wavelength of the photon by an amount called the Compton shift . The maximum magnitude of this wavelength shift is h / m e c , which is known as the Compton wavelength . For an electron, it has a value of 2.43 × 10  m . When the wavelength of the light is long (for instance, the wavelength of the visible light is 0.4–0.7 μm) the wavelength shift becomes negligible. Such interaction between

17680-563: Was Thomson's graduate student, performed the first experiments but he died soon after in a motorcycle accident and is rarely mentioned. De Broglie's prediction of a wave nature for electrons led Erwin Schrödinger to postulate a wave equation for electrons moving under the influence of the nucleus in the atom. In 1926, this equation, the Schrödinger equation , successfully described how electron waves propagated. Rather than yielding

17816-416: Was able to qualitatively explain the chemical properties of all elements in the periodic table, which were known to largely repeat themselves according to the periodic law . In 1924, Austrian physicist Wolfgang Pauli observed that the shell-like structure of the atom could be explained by a set of four parameters that defined every quantum energy state, as long as each state was occupied by no more than

17952-734: Was caused by the rays striking the tube walls. Furthermore, he also discovered that these rays are deflected by magnets just like lines of current. In 1876, the German physicist Eugen Goldstein showed that the rays were emitted perpendicular to the cathode surface, which distinguished between the rays that were emitted from the cathode and the incandescent light. Goldstein dubbed the rays cathode rays . Decades of experimental and theoretical research involving cathode rays were important in J. J. Thomson 's eventual discovery of electrons. Goldstein also experimented with double cathodes and hypothesized that one ray may repulse another, although he didn't believe that any particles might be involved. During

18088-672: Was governed by the inverse square law . After studying the phenomenon of electrolysis in 1874, Irish physicist George Johnstone Stoney suggested that there existed a "single definite quantity of electricity", the charge of a monovalent ion . He was able to estimate the value of this elementary charge e by means of Faraday's laws of electrolysis . However, Stoney believed these charges were permanently attached to atoms and could not be removed. In 1881, German physicist Hermann von Helmholtz argued that both positive and negative charges were divided into elementary parts, each of which "behaves like atoms of electricity". Stoney initially coined

18224-426: Was later explained by the theory of quantum electrodynamics , developed by Sin-Itiro Tomonaga , Julian Schwinger and Richard Feynman in the late 1940s. With the development of the particle accelerator during the first half of the twentieth century, physicists began to delve deeper into the properties of subatomic particles . The first successful attempt to accelerate electrons using electromagnetic induction

18360-415: Was made in 1942 by Donald Kerst . His initial betatron reached energies of 2.3 MeV, while subsequent betatrons achieved 300 MeV. In 1947, synchrotron radiation was discovered with a 70 MeV electron synchrotron at General Electric . This radiation was caused by the acceleration of electrons through a magnetic field as they moved near the speed of light. With a beam energy of 1.5 GeV,

18496-413: Was originally coined by George Johnstone Stoney in 1891 as a tentative name for the basic unit of electrical charge (which had then yet to be discovered). The electron's charge was more carefully measured by the American physicists Robert Millikan and Harvey Fletcher in their oil-drop experiment of 1909, the results of which were published in 1911. This experiment used an electric field to prevent

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