Electrons In Vacuum Research Articles

Tunnel transitions, vacuum background and scattering processes in quantum electrodynamics

It is shown that in external fields there may occur an excitation (deformation) of the vacuum state of the electron-positron system which is not accompanied by the processes of real electron-positron pair creation. In the case of the excited vacuum the wavefunctions of the vacuum electrons have both negative-frequency and positive-frequency components. The true meaning of the Klein mechanism of vacuum polarisation is that the 'bare' electron states are 'dressed' by the applied field and as a result the vacuum passes from the ground state to an excited one without creating real pairs. From the real pair creation criterion obtained it is inferred that no real pairs can be created by an arbitrary static field. It follows from the results presented that induced emission of the excited vacuum background is possible, i.e. transitions of the collective vacuum vibrations to the single quasi-particle states may occur. Deformation of the vacuum cannot be correctly taken into account within S-matrix scattering theory because in the latter this process is always interpreted as real pair creation.

Ultimate bistability: Hysteretic resonance of a slightly-relativistic electron

It was recently predicted by us that cyclotron resonance of free electrons in vacuum and conduction electrons in semiconductors may exhibit bistable and hysteretic behavior which is due to the relativistic mass-effect (or pseudo relativistic-in semiconductors). Consistent with this prediction, the hysteretic cyclotron resonance of a trapped single electron in vacuum has recently been experimentally observed by Gabrielse et al. A preliminary estimate shows that their experimental results are consistent with the relativistic nature of the observed hysteresis. In this paper we consider this phenomenon as ultimate bistability since it is based on the most fundamental mechanism of nonlinearity (the relativistic mass-effect), involves the interaction of an EM wave with the simplest single elementary particle, and exhibits the first known intrinsic bistability with no macroscopic optical feedback. We also show that a hysteretic resonance of a Single electron based on relativistic effects is feasible also in a parabolic potential (with no magnetic field required to attain a resonance).

Semirelativistic Behavior of Electrons in InSb in Crossed Magnetic and Electric Fields

Cyclotron-resonance experiments on conduction electrons in InSb are performed in crossed magnetic and electric fields with use of a metal-oxide-semiconductor structure. The data are successfully described on the basis of a three-level k\ifmmode\cdot\else\textperiodcentered\fi{}p band model. The electron behavior in crossed fields is interpreted as a spectacular example of an analogy between electrons in narrow-gap semiconductors and relativistic electrons in vacuum.

A high-energy, laser accelerator for electrons using the inverse Cherenkov effect

A laser method for accelerating electrons is described, based on the inverse Cherenkov effect in a gas. The laser fields are in the form of a cylindrical cone of plane waves on whose axis travel the electrons, with the cone angle and the gas refraction index such that each electron sees constant fields in time. Expressions are obtained relating the overall energy transfer to total laser power and wavelength, and to gas index and interaction length. With laser powers now available, energy increments of tens of GeV are possible. For comparative purposes, a related alternative scheme involving electrons in vacuum and evanescent laser fields is also analyzed. It is found that the method applies particularly well to adding energy to the electron bunches produced by large microwave accelerators, as collision effects are less troublesome at high injection energies.

Piezoelectricity and acoustoelectronics

Abstract Acoustoelectronics is based both in its conceptional and experimental aspects on the piezoelectric effect discovered by J. Curie and P. Curie. This paper reviews the research on acoustoelectronics which has been carried out at A. F. loffe Physico-Technical Institute in Leningrad. Three basic types of acoustoelectron interactions are considered: (i) interaction of bulk acoustic waves in a piezoelectric semiconductor with free charge carriers; (ii) interaction of surface acoustic waves in a piezodielectric crystal with free carriers in an adjacent semiconductor and (iii) interaction of surface acoustic waves in a piezoelectric crystal with free electrons in vacuum. The main characteristic features of the acoustoelectron interactions are illustrated by the experimental results obtained with well known piezoelectric crystals such as CdS, Te, InSb, SiO2, LiNbO3. Both linear and nonlinear acoustoelectron effects are described.

Particle acceleration in the drift orbit cyclotron

The drift orbit cyclotron was investigated both theoretically and experimentally. A drift orbit cyclotron was designed and constructed, and acceleration experiments using electrons in high vacuum were performed. Theoretical calculations using the guiding center approximation match the experimental results. Improvement of the acceleration efficiency was observed by using the stochastic acceleration technique.

Reactivity of plasma-treated SiO 2 against O 2: An EPR study

During plasma treated of SiO 2 (dehydrated at 700°C in high vacuum) electrons become trapped at the surface and in the bulk. The captured electrons from the well known E í centre, an F-like electron centre with the unpaired electron mainly in an s-type orbital, and CO 2 − which comes from carbon impurities. Adsorption of O 2 (partial pressure 5 × 10 -3 torr ⩽ po 2 ⩽ 10 −1 torr) gives O 2 − species that depend on the adsorption temperature, characterized by the following g-values: g 1 = 2.069, g 2 = 2.000m T ads = 300 K; g 1 = 2.039, g 2 = 2.007, g 3 = 2.002, T ads = 77 K.

The emission of electrons from glass induced by a strong electric field and the mechanism of the silent electric discharge

Ordinary borosilicate (Pyrex) glass was found to emit electrons in vacuum when a sufficiently strong electric field was applied. Two distinct phenomena were observed. First, emission from the surface of a sharp glass tip occurred with a macroscopic field of about 5 × 109V m-1applied, but the electric stress was then great enough to shatter the glass in a short time. Second, emission from active sites on glass tubes occurred at macroscopic fields (F) of about 5 × 106V m-1. The number of emitting sites increased with applied field and was about 0.5 mm-2with a field of 107V m-1. Emission from these sites was essentially the same under ordinary vacuum conditions and under ultra-high vacuum conditions. The current from active sites under vacuum conditions increased nearly exponentially withF½at constant temperature, and nearly exponentially with temperature at constant field. Active emitting sites on glass were very stable to chemical cleaning processes and to ion bombardment and electric discharges, in sharp contrast to emitting sites on thin metal wires. The sites on glass also emitted electrons in the presence of gases, but no emission of negative ions was noted in magnetic deflexion experiments. Current-voltage relations in the presence of gases were measured. With oxygen present, ozone was formed using glass tubes with either a. c. or d. c. applied. However, with a silica tubes ozonizer, ozone was formed with a. c. applied but not with d. c. applied. Ozone was also formed in an electric discharge between a thin metal wire (thin enough to act as a field emitter) and an outer metal cylinder. This ozonizer was compared with the glass ozonizer and energy efficiencies were measured. It is proposed that the external electric field causes emission of single electrons from isolated sites on glass and that the emitted electron interacts with the electron hole left behind at the surface. Equations are deduced for the case when the interaction is mainly between the electron and the electron hole rather than between the electron and its image. A model of field enhanced thermionic emission from sites with low work function (Schottky emission) is found to explain the results for emission from active centres on glass, and the field intensification factorβappears to be about unity. Although Schottky emission is considered more important than field emission for the fields used with glass tubes, calculations show that field emission becomes more important at higher electric fields. The emission of electrons is considered to be important in initiating the silent electric discharge.

Work function measurements on (100) and (110) surfaces of silver

(100) and (110) single crystals of silver were cleaned by electron and argon-ion bombardment in ultra-high vacuum. The work functions of the bulk crystals, and of silver films formed upon them by autoepitaxy, were determined photoelectrically. The bulk crystals had work functions of (4.64 ± 0.02) eV and (4.52 ± 0.02) eV respectively. The effect of the deposition of silver films was to reduce the work function, but continued cycles of deposition and annealing at 500 to 600 K caused the work function to return to a value very close to that of the bulk crystal. An annealed film of silver deposited in stages on a mica substrate at 425 K had a work function of (4.72 ± 0.02) eV, corresponding to that of the (111) silver surface. If the mica remained at room temperature during deposition, the work function was about 4.5 eV. The work function of a thick polycrystalline film of silver on quartz was (4.26 ± 0.02) eV. The results support the Smoluchowski correlation of work function with surface atom density. (100)- und (110)-Silbereinkristalle werden mit Elektronen- und Argon-Ionen-Bombardement im Ultra-Hochvakuum gereinigt. Die Austrittsarbeit der Volumenkristalle und der Silberschichten, die auf ihnen auto-epitaktisch aufgebracht wurden, wurden photoelektrisch bestimmt. Die Volumenkristalle zeigten Austrittsarbeiten von (4,64 ± 0,02) eV bzw. (4,52 ± 0,02) eV. Der Einfluß der Aufbringung der Silberschichten bestand in der Verringerung der Austrittsarbeit, jedoch verursachte ein fortgesetzter Zyklus von Aufbringung und Temperung bei 500 bis 600 K, daß die Austrittsarbeit zu einem Wert zurückkehrte, der sehr nahe an dem der Volumenkristalle lag. Eine getemperte Silberschicht, die stufenweise auf einem Glimmersubstrat bei 425 K aufgebracht wurde, zeigte eine Austrittsarbeit von (4,72 ± 0,02) eV entsprechend der der (111)-Silberoberfläche. Wenn die Glimmerunterlage während der Aufbringung auf Zimmertemperatur gehalten wurde, lag die Austrittsarbeit bei ungefähr 4,5 eV. Die Austrittsarbeit von dicken polykristallinen Silberschichten auf Quarz betrug (4,26 ± 0,02) eV. Die Ergebnisse bestätigen die Korrelation von Smoluchowski zwischen der Austrittsarbeit und der Atomdichte an der Oberfläche.

On the lifetime of the muon state of the electron-muon mass doublet

In a previous paper the electron and muon masses were derived by combining the author’s general relativistic derivation of the inertial masses of spinor particles from the geometrical field and his model of the « physical vacuum » (from a self-consistent field theory of electrodynamics) in terms of an ideal gas of electron-positron pairs in a particular state that was derived from the theory. It was predicted earlier that in this field theory spinor particles occur in mass doublets. In the electron-muon case, the observation of the « heavy electron » (muon) is a consequence of quadrupolar excitation of the physical vacuum of pairs—correspondingly altering the geometrical field in the vicinity of the observed electron, thereby making it more inertial. In this paper, the lifetime of the heavy electron in this physical vacuum will be determined, de-excitation occurring by the transferral of electromagnetic energy from this heavy electron to the pairs of the physical vacuum by means of a quadrupolar transition. To facilitate the calculation with time-dependent perturbation theory, use is made of Fermi’s multiple-meson production theory, and the improvisation of his theory for break-up reactions by the author. In this way, the ensuing quantitative analysis yields a lifetime for the heavy electron that is of the order of 2.09·10-6 s, which is within 5% of the observed muon decay rate. It is then shown how the present theory, in which electromagnetic variables are in terms of 2-component spinor fields, explains the reaction Μ → e++Ν in terms of a process that is purely electromagnetic and does not entail neutrinos.

EXCITATION OF ELECTRONS IN SOLIDS BY RELATIVELY SLOW ATOMIC PARTICLES

I. Introduction 332 II. Excitation of Electrons Due to the Internal Energy of the Atomic Particle-plus-solid System and Potential Ejection of Electrons 332 III. Kinetic Ejection of Electrons in Vacuum 342 IV. Radiative (Induced) Conductivity of Semiconductors Bombarded with Ions 353 V. Excitation of Luminescence by Ion Bombardment of Solids, and Ionoluminescence 358 VI. Conclusion 362 Cited Literature 364

Radiation resistance and irreversible power of antennas in gyroelectric media

In recent years, many investigators have been working on the problem of calculating the radiation resistance of a dipole antenna immersed in an anisotropic medium [1]. The central difficulty of their method of calculation is that it yields an infinite value for the radiation resistance. They hare attributed this infinity to the infinitesimal size of the source, and have suggested that if the source were of finite spatial extent the difficulty would not arise. It is our contention that the difficulty is of a more basic nature and is not due to the size of the source but to the method of calculation. The purpose of this letter is to show that if the radiation resistance is calculated with proper conformity to the thermodynamical laws of reversibility and irreversibility, the value of the radiation resistance will turn out to be finite. Clearly, radiation resistance is on the same footing as ordinary circuit resistance in the sense that they both are measures of irreversible power, and hence in calculating radiation resistance it is necessary that only the irreversible part of the power be used. Accordingly, we shall construct an expression for the irreversible part of the power emitted by a source, and show that the expression so constructed is finite and hence leads to a finite value for the radiation resistance. To construct the required expression, we recall that in the case of an accelerating point electron in vacuum, the combination of half the retarded minus half the advanced field is free from singularity [2] and corresponds to the irreversible power radiated by the electron [3]. We shall extend this idea of taking a combination field to the case of a monochro matic source Re(Je^(iWt)) radiating into a lossless anisotropic medium.

Degradation of polytetramethylene oxide. II. Ionising radiation

AbstractAnalysis of the solubility behaviour of polytetramethylene oxide after exposure to high energy electrons in vacuum indicates a ratio of main chain scissions to cross‐links of 0.37. These changes are accompanied by the evolution of hydrogen (G(H2) = 0.8) and traces of other gases. The viscosity changes of the irradiated polymer and the preferential destruction of week links present in the polymer chain are discussed.

Space charge limited and emitter current limited injections in space charge region of semiconductors

If, in a space charge region of a semiconductor device, a unipolar drift current is a main component of the total current, an analogy with motion of electrons in vacuum exists. In the space charge limited emission, injection of minority carriers is limited by space charges, as in a punched-through p-n-p diode. On the other hand, in a transistor, minority carriers are injected into the depletion layer between the base and the collector, after diffusion in the neutral base region. This injection is limited by emitter current, and this mode of injection corresponds to a temperature limited emission in a vacuum tube. In this paper, equations of minority carrier impedances will be calculated in both these cases, and negative resistances can be expected at some transit angles. Then a generalized equation, which includes these two modes of injections as special cases, will be obtained. This generalized equation corresponds to the Llewellyn-Peterson equation of vacuum tubes, which include the space charge limited emission and the temperature limited emission as special cases.

Meissner Effect and the Self-Energy of the Photon

It is pointed out that a close analogy exists between the Meissner effect of the superconductor and the self-energy of the photon. Based on this analogy, it is shown that a gauge invariant self-energy can be obtained by introducing the contributions from the collective motion of the vacuum electrons, just as the gauge invariant theory of the Meissner effect can be obtained by introducing the contribution from the plasma oscillation. Implications of the nonvanishing self-energy are discussed. (auth)

The influence of the temperature of irradiation on the formation of polymer networks

A sample of high-density polyethylene (Marlex 50) was irradiated with 4- Mev electrons in vacuum at 25 and --196 deg C. The results show that, on lowering the temperature, the yield of crosslinks is scarcely affected, while the yield of fractures is increased. It is concluded that the hydrogen-crosslinking mechanism is still valid. (D.L.C.)

Space-Charge Limited Hole Current in Germanium

A situation can arise in semiconductors similar to the space-charge limited emission of electrons in vacuum. The theory of Shockley and Prim for this phenomenon has been extended to the high field case using the approximation that the drift velocity of the carriers is $v=\ensuremath{\mu}{(E{E}_{0})}^{\frac{1}{2}}$, where $\ensuremath{\mu}$ is the low field mobility, $E$ the electric field, and ${E}_{0}$ the "critical field." For this approximation the current density analogous to Child's law for a plane parallel diode is $J=\frac{(\frac{2}{3}){(\frac{5}{3})}^{\frac{3}{2}}K\ensuremath{\mu}{{E}_{0}}^{\frac{1}{2}}{{V}_{a}}^{\frac{3}{2}}}{{w}^{\frac{5}{2}}},$ where ${V}_{a}$ is the potential across a diode of thickness $w$ and $K$ is the dielectric constant in mks units. Good agreement between theory and experiment for hole flow in germanium at liquid air temperature has been obtained, using values of $\ensuremath{\mu}$ and ${E}_{0}$ obtained independently by Ryder.

The Effect of a Hydrogen Atmosphere on the Velocity Distribution Among Thermionic Electrons

The thermionic current from a tungsten or platinum filament to a coaxial cylindrical electrode was measured for different retarding potentials first in vacuum and then in hydrogen keeping the temperature of the filament constant. The heating current was made intermittent to eliminate the magnetic field and the potential drop along the filament when the thermionic current was being measured. The filament temperature was kept constant to $\frac{1}{10}$ percent by a Wheatstone bridge arrangement of which the filament was made one arm. Filament temperatures ranging from 1520\ifmmode^\circ\else\textdegree\fi{}K to 1990\ifmmode^\circ\else\textdegree\fi{}K, and pressures of hydrogen from 0 to 0.25 mm Hg were used. The distribution of velocities among the electrons in vacuum and in hydrogen was found to follow Maxwell's law; and contrary to the experience of former observers the temperature calculated from the Maxwellian distribution was found to be the same for the case of a vacuum as for that where hydrogen was present to an accuracy higher than 0.7 percent which is within the accuracy of the experimental data. Moreover, the temperature so calculated was for all cases in close agreement with the filament temperature estimated from data of Forsythe and Worthing for tungsten and those of Pirrani for platinum. The maintenance of thermal equilibrium between the electrons and the filament in hydrogen suggests the elastic nature of the collisions between the electronsand the hydrogen molecules.

Scattering of Electrons in Ionized Gases

Velocity distribution of electrons in low pressure discharges from hot cathodes.---Analysis of the current received by a collector placed opposite a hot cathode indicates that there are three groups of electrons present; (1) primary electrons which retain practically all the momentum they acquired in passing through the positive ion sheath around the cathode; (2) secondary electrons moving in random directions with a Maxwellian velocity distribution corresponding to a temperature roughly proportional to the energy of the primaries (200,000\ifmmode^\circ\else\textdegree\fi{} for 100 volt primaries) and approximately independent of the nature or pressure of the gas or the current density; (3) ultimate electrons having a Maxwellian distribution of velocities corresponding to a much lower temperature than that of the secondaries, a temperature which is independent of the current density or the voltage of the primary electrons and which varies with the gas used and decreases slowly as the pressure is raised. The number of ultimate electrons is roughly 1000 times that of the primaries and secondaries for mercury vapor, although relatively less numerous in the case of hydrogen. In the uniform positive column of arcs only ultimate electrons are present.The velocity distribution of the primary electrons may be resolved into a drift velocity normal to the cathode surface and a random motion with a Maxwellian distribution corresponding to a temperature which varies approximately with the square of the current and is a maximum at a mercury vapor pressure of about 0.6 bar, falling to a low value at 8 bars, and is considerably higher with 35 volts accelerating potential than with 80 volts. Under favorable conditions with 40 mil-amp. this temperature may rise to 80000\ifmmode^\circ\else\textdegree\fi{} and there are then appreciable numbers of these primaries which can reach a collector charged to a potential as much as 40 volts below that of the cathode. Experiments with two crossed electron beams prove that the secondary and ultimate electrons, directly or indirectly, are responsible for very little if any of the scattering.A study of the ultimate electrons in the positive column of a low voltage mercury arc shows that the Maxwellian velocity distribution corresponding to a high temperature (30000\ifmmode^\circ\else\textdegree\fi{}) is maintained in a small tube in spite of the fact that the negatively charged walls of the tube constantly tend to disturb this distribution by selective removal of the faster electrons. The number of collisions of the electrons with each other and with atoms were far too few to maintain the observed distribution. Measurements of the mobilities of electrons in arcs and of the electron concentration differences produced by a transverse magnetic field gave values for the mean free path only 1/10 as great as the values determined by a direct method. These results all indicate that the electrons in low pressure arcs suffer many changes of momentum during the time intervals between successive collisions between atoms, ions or electrons.Mechanism of electron scattering.---After analyzing the effects to be expected when a beam of primary electrons encounters a cloud of stationary electrons or a cloud of particles of small mass but of high temperature, it appears that the experimental results for the ratio of the scattering to the average retardation of the beam was best accounted for by collisions with a cloud of radiation quanta, a kind of Compton effect. The observed scattering is, however, about ${10}^{16}$ times greater than a normal Compton effect would give It is suggested that the joint action of excited atoms and radiation may multiply the Compton effect sufficiently, or it may be that the presence of a free electron within a distance of a wave-length from an excited atom may greatly increase the probability of a quantum jump and that momentum is delivered to the electron in the process. In arcs the ultimate electrons may be in a kind of thermal equilibrium with radiation and excited atoms.Scattered electrons in high vacuum.---In connection with a study of the Barkhausen-Kurz effect and in a magnetron with negatively charged end plates, exidence of the presence of electrons with abnormally high speeds has also been obtained. These have been explained as due to electric oscillations, but the effects have also been obtained when oscillations are not present. This seems to indicate that electron scattering similar to that observed in low pressure gases can also occur in high vacuum.