Transport equations for a weakly ionized electron gas.
Electron traceless pressure and heat flow for weakly ionized electron gas in DC magnetic field assuming electron-neutral collisions dominate
Tanenbaum, B. S.↗
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Behavior of the ionization cross section in collisions of high-energy electrons with hydrogenic atoms.
Hydrogenic atoms ionization by high energy electrons, discussing cross sections for ejected electrons and total energy
Omidvar, K.↗
Resonance scattering and the drift motion of electrons through gases. II
Resonance scattering and drift motion of electrons in gases under pressure, determining ion state lifetime and mean electron-molecule collision frequency for trapping collisions
Frommhold, L.↗
Electrical and thermal conductivity in a superdense lattice. I
Electrical and thermal conductivities in white dwarf stars cores and neutron stars outer layers, calculating electron-photon collisions transition probability
Solinger, A. B.↗
Computer-plotter studies of vibrational effects in ion-dipole collisions - Classical tunneling
Computer graphics of vibrational effects in ion molecule collisions including electron tunneling oscillations, nuclear capture, and molecular oscillations and relaxation
Canright, B., Jr.↗
Plasma phenomena at magnetic neutral points
A model of the plasma focus is considered, in which large axial electric fields are induced by the imploding current sheet during the final few nanoseconds of the collapse phase. This field provides a mechanism for creation of a beam of electrons of highly suprathermal energies. For this beam, the bremsstrahlung radiation is calculated, which is expected either from electron-deuteron collisions in the focused plasma itself or from the beam as it reaches the walls of the device. Comparison with experimental results indicates that the walls are the more likely source of these hard X-rays and also find qualitative agreement of the expected angular distribution of X-rays with experiment.
Sturrock, P. A.↗
Production of a large, quiescent, magnetized plasma
An experimental device is described which produces a large homogeneous quiescent magnetized plasma. In this device, the plasma is created in an evacuated brass cylinder by ionizing collisions between electrons emitted from a large-diameter electron gun and argon atoms in the chamber. Typical experimentally measured values of the electron temperature and density are presented which were obtained with a glass-insulated planar Langmuir probe. It is noted that the present device facilitates the study of phenomena such as waves and diffusion in magnetized plasmas.
Landt, D. L.↗
Comment on the relation between the nonadiabatic coupling and the complex intersection of potential energy curves
Simple relations are discussed that provide a correspondence between the complex intersection of two potential surfaces and the nonadiabatic coupling matrix element between those surfaces. These are key quantities in semiclassical and quantum mechanical theories of collision induced electronic transitions. Within the two state approximation, the complex intersection is shown to be directly related to the location and magnitude of the peak in the nonadiabatic coupling. Two cases are considered: the avoided crossing between two potential surfaces; and the spin orbit interaction due to a P-2 halogen atom. Comparisons are made between the results of the two-state model and the results of ab initio quantum chemical calculations.
Jaffe, R. L.↗
Comment on the relation between the nonadiabatic coupling and the complex intersection of potential energy curves
Simple relations are discussed that provide a correspondence between the complex intersection of two potential surfaces and the nonadiabatic coupling matrix element between those surfaces. These are key quantities in semiclassical and quantum-mechanical theories of collision-induced electronic transitions. Within the two-state approximation, the complex intersection is shown to be directly related to the location and magnitude of the peak in the nonadiabatic coupling. Two cases have been considered: (1) the avoided crossing between two potential surfaces, and (2) the spin-orbit interaction due to a 2P halogen atom. Comparisons are made between the results of the two-state model and the results of ab initio quantum chemical calculations.
Jaffe, R. L.↗
Production of O(-) from CO2 by dissociative electron attachment
Dissociative electron attachment cross-section measurements for the production of O(-) from CO2 are performed using a crossed target-beam - electron-beam collision geometry and a quadrupole mass spectrometer. The relative flow technique is used in determining the absolute values of the cross sections. The attachment energies corresponding to the five cross-section maxima are given. They are 4.4 + or - 0.1, 8.2 + or - 0.1, 13.0 + or - 0.2, 16.9 + or - 0.2, and 19.4 + or 0.2 eV. Also given are the cross sections at these maxima: 1.43 x 10 to the -19th sq cm, 4.48 x 10 to the -19th sq cm, 8.1 x 10 to the -21st sq cm, 8.1 x 10 to the -21st sq cm, and 1.2 x 10 to the -20th sq cm, respectively.
Orient, O. J.↗
Electrostatic waves and anomalous transport in the solar wind
In situ measurements of fluctuation spectra and particle distribution functions have now been carried out throughout interplanetary space. The link between these observations is established by theories of wave particle interaction. Linear instability analysis for the actual nonMaxwellian particle distribution functions and an examination of the velocity dependence of microscopic diffusion coefficients form the basis of such an investigation. It is described in more detail for the short wavelength, ion acoustic like turbulence which is found by linear instability analysis to correspond to the observed electrostatic fluctuations. Of the transport processes associated with these fluctuations, electron heat conduction and electron ion energy transfer are of particular importance for macroscopic solar wind expansion. These effects are studied with the aid of an anomalous transport theory. This theory (Dum, 1978 a,b) is based on the dominance of elastic scattering of electrons by fluctuations, similar to (enhanced) electron ion collisions. It has a much wider range of applicability than classical transport theory, which assumes dominance of Coulomb collisions for elastic and inelastic scattering.
Dum, C. T.↗
Positron production by a hot, young pulsar
The paper considers a way of positron production in pulsars: pair production from electron-photon collisions. It is shown that this process must be the dominant one for a young pulsar when its surface temperature is around 10-million K. This model is applied to the observed positron flux coming from the Galactic Center and it is shown that a pulsar with parameters close to those of the Crab at birth can explain, in principle, the flux.
Brecher, K.↗
Measurement of partial pressures in vacuum technology and vacuum physics
It is pointed out that the measurement of gaseous pressures of less than 0.0001 torr is based on the ionization of gas atoms and molecules due to collisions with electrons. The particle density is determined in place of the pressure. The ionization cross sections for molecules of various gases are discussed. It is found that the true pressure in a vacuum system cannot be determined with certainty if it is unknown which gas is present. Effects of partial pressure determination on the condition of the vacuum system are discussed together with ion sources, systems of separation, and ion detection.
Huber, W. K.↗
Energy partitioning in the Io plasma torus
The Io plasma torus, which emits substantial amounts of EUV radiation from multiply ionized oxygen and sulfur, represents one of the significant discoveries of the Voyager 1 mission. The present study is concerned with the effects of various physical processes on the density and energy partitioning of the Io plasma torus. For the ions the dominant effects, which have different relative importance in different parameter regimes, are electron impact ionization, charge exchange, electron-ion collisions, and confinement time loss. Attention is given to a physical model, the solution of the quasi-linear equations, the obtained results, and an interpretation of observations in relation to the model results.
Smith, R. A.↗
An analysis of electromagnetic coupling and eigenfrequencies for microwave electrothermal thruster discharges
This paper discusses the basic approach to developing a comprehensive electromagnetic model for a microwave electrothermal discharge. The discharge and surrounding region are modeled as a section of waveguide loaded with a uniform, cold, lossy plasma. A characteristic equation has been derived describing all possible system modes. In particular the TM(01) mode is numerically solved. Propagation and attenuation constants for the TM(01) mode are found numerically for a given range of electron-neutral collision frequencies and plasma densities. Results are used to interpret a number of experimental observations in helium. Specifically, they are used to explain high coupling efficiencies and ease of cavity tuning at high pressures.
Frasch, L. L.↗
The contribution to the gamma-ray background from a superposition of 3C 273-like jet sources
Recent theories suggest that quasar jets may produce the gamma-ray emission observed in sources such as 3C 273. One of these theories is tested to see if it is consistent with observations of the gamma-ray background. Quasar jets are taken as the source of this radiation, each with the spectrum of the nearby quasar 3C 273, and with an evolution in time based on a model for the observed gamma-rays of 3C 273. In that model, a plasma jet interacts with the ambient intergalactic gas to produce (from nuclear collisions) secondary electrons which lead to isotropic bremsstrahlung gamma-rays, and ultimately to a double radio source. It is shown that the gamma-ray background can be modeled in general as a superposition of such discrete sources of various redshifts. The results are consistent with the observed background intensity and spectral form; of course, there are uncertain and adjustable parameters.
Sadun, Alberto C.↗
Ab initio R-matrix calculations of e+-molecule scattering
The adaptation of the molecular R-matrix method, originally developed for electron-molecule collision studies, to positron scattering is discussed. Ab initio R-matrix calculations are presented for collisions of low energy positrons with a number of diatomic systems including H2, HF and N2. Differential elastic cross sections for positron-H2 show a minimum at about 45 deg for collision energies between 0.3 and 0.5 Ryd. The calculations predict a bound state of positronHF. Calculations on inelastic processes in N2 and O2 are also discussed.
Danby, Grahame↗
The G value in plasma and radiation chemistry
The application of the G-value concept to plasma chemistry is considered. A general formula which expresses the G value for a general reaction in terms of experimentally controllable parameters is derived by applying simple gas-dynamic theory to a plasma reactor with straight walls. The formula expresses the G value as a function of the electrical power absorbed, the fraction of molecules transformed, and the flow rate of the gas entering the reactor. The formula was applied to the ammonia plasma radio-frequency discharge data of d'Agostino et al. (1981); the results showed that the G(-NH3) value lies in the range of 6.0-20 molecules/100 eV, depending on the conditions. This similarity of the G(-NH3) value with Peterson's (1974) range 2.7-10 found for the gas-phase radiolysis of ammonia, suggests that there might be a common reaction mechanism initiated by inelastic electron-molecule collisions.
Baird, James K.↗