Possible ionic systems for the development of a pulsed laser on the basis of ion-ion recombination: I. Recombination with negative halogen ions

Possible pairs of positive and negative ions for development of a pulsed laser based on ion-ion recombination with participation of negative halogen ions are considered. The most appropriate pairs of ions are indicated. The effect of additional kinetic energy of the atoms formed during the ion-ion recombination is discussed.     

Pulsed population inversion in recombination of positive metal ions with negative ions of sulfur,selenium, and tellurium

Ion-ion recombination of positive ions of 14 metals with negative ions of sulfur, selenium, and tellurium is considered. The energy levels of metal atoms predominantly populated in the process of ion-ion recombination are estimated. The possibility of creating the population inversion in the afterglow of a pulsed discharge on some atomic transitions is discussed along with realization of noncoherent sources of radiation.     

Fundamentals and applications of ion-ion plasmas

Ion-ion plasmas can form in the late afterglow of pulsed discharges or downstream of continuous wave discharges in electronegative gases. In ion-ion plasmas, negative ions replace electrons as the negative charge carriers. In the absence of electrons, ion-ion plasmas behave quite differently compared to conventional electron-ion plasmas. Application of a radio frequency bias to a substrate immersed in an ion-ion plasma can be used to extract alternately positive and negative ions, thereby minimizing charging on device features during micro-device fabrication. Ion-ion plasmas are also important in negative ion sources, dusty plasmas, and the D-layer of the earth's atmosphere.     

Simple analytic relations for estimating parameters of the positive column of an electronegative glow discharge in a halogen-containing gas mixture

Asymptotic analysis of the continuity equations for the positive charge plasma of a low- and moderate-pressure dc electronegative discharge is performed under the simple assumption of independence of the rates of plasma-chemical processes from coordinates. As a novelty, the ion diffusion is taken into account for the case when the ion-ion recombination dominates among the perishing mechanism of negative ions. The resultant simple analytic expressions make it possible to estimate (with an error not exceeding 15–25%) the geometrical parameters of spatial distributions of charged particle concentrations in this plasma, as well as the energy parameters, without resorting to complicated numerical simulation.     

Evolution of the density profiles and flows of charged particles during the diffusive decay of an electronegative gas plasma

Different scenarios of the spatiotemporal evolution of the parameters of the diffusive decay of a pulsed electronegative gas plasma in the absence of plasma chemical processes are studied. It is shown that nonlinear diffusion in a plasma with negative ions occurs in several stages. The rate of electron density decay increases with time and, in the beginning of the second stage, almost all the electrons escape from the discharge volume. On the other hand, the ion density profile is smoothed out due to ion-ion ambipolar diffusion and the flow of negative ions toward the wall is absent in the first stage of decay. In the second stage, the main diffusion mode is first established and then the ion-ion (electronless) plasma decays exponentially with a characteristic time determined by ion-ion ambipolar diffusion.     

A Survey of the Electron and Ion Transport Properties of SF6

A compilation of the available data on some of the basic transport properties of sulfur hexafluoride (SF6) is presented. The properties considered are a) electron ionization, attachment, detachment and diffusion coefficients, and electron drift velocity; b) positive and negative ion mobilities, negative ion diffusion, and ion-ion recombination coefficients; and c) secondary ionization coefficients. Approximate analytical representations of the data are also given.     

Numerical Simulation of a DC-Glow-Discharge in an Electronegative Gas

A one-dimensional continuum model is presented for a dc-glow-discharge in an electronegative gas between parallel plates. It is based on the local balance equations for particle densities and fluxes of electrons, positive and negative ions, the local electron energy balance and the Poisson equation for the self-consistent electric field. These equations are supplemented by suitably chosen boundary conditions and are solved by the finite difference procedure HEMODES (HEnyey Method Ordinary Differential Equation Solver) which, in particular, can successfully handle the singular point occuring if the inertia term in the ion momentum balance equation is taken into account. Since not all data needed within this treatment for the simulation of realistic electronegative gases were available, a fictitious argon-like gas has been considered which nevertheless can demonstrate the characteristic features of such a discharge. In particular, the influence of variations of the attachment and the ion-ion recombination coefficients on the physical variables has been studied.     

Lower hybrid waves in plasmas with negative ions

The ion-ion hybrid mode, with frequencies ω≈(ω_c+ω_c-)^1/2, is briefly analyzed for a warm plasma containing positive ions (gyrofrequency ω_c+), negative ions (gyrofrequency ω_c-), and electrons. Experiments with SF₆ ^- as the negative ion are proposed     

Recombination of a coulomb plasma and nonbinary interaction effects

A theory has been constructed for the recombination of a Coulomb plasma with allowance for the anomalous nature of diffusion along the energy axis in the negative energy region of Coulomb particles. These anomalies, which were revealed earlier by first-principles numerical simulation, are due to the dynamic memory of a classical Coulomb plasma. Two kinetic models are presented. The first takes random collisions with a hypothetical gas of two-level atoms into account. Comparison of the results of this model with first-principles calculations shows that the characteristic of the diffusion coefficients is missing. The second model takes the discrete nature of bound states into account. Calculations show that for an electron-hole plasma the recombination rate deviates substantially from the results of conventional theory only when either the recombination time is very short or the effect is masked by radiative recombination. For ion-ion plasma, the deviations from conventional recombination theory run to several orders of magnitude. This is of interest in relation to ball lightning.Institute of General Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 68–89, January, 1993.     

Cross-Sections,Rate Constants and Transport Coefficients in Silane Plasma Chemistry

This paper presents a critical review of the basic data concerning the physics and chemistry of low pressure SiH₄ glow discharges used to deposit hydrogenated amorphous silicon films (a-Si:H). Starting with an updated table of thermochemical data, we analyze the gas-phase elementary processes consisting of i) electron-molecule collisions, ii) ion-molecule collisions, iii) neutral-neutral collisions, iv) other electron and ion collisions involving electron-ion and ion-ion recombination, electron attachment on radicals and detachment of anions, and v) cluster growth kinetics in dusty plasmas. Experimental data or theoretical estimates are given and discussed in terms of cross-sections, collision and reaction rate constants, and transport coefficients. We also analyze the surface processes and reaction probabilities of ions, radicals and molecules.     

A pulsed ion-ion recombination laser

A new mechanism of pulsed laser oscillation based on ion-ion recombination is proposed. The advantages of utilizing this mechanism in a pulsed mode are considered, and the expected characteristics of the proposed lasers are estimated.     

Ion aging effects on the dissociative-attachment instability in CO2 lasers

Onset of the dissociative-attachment instability requires that the rate coefficient for electron detachment (k _d) from negative ions be below a critical value. The predominant negative and positive ions in a CO₂N₂He gas-discharge plasma are known to change with time. As secondary by-products form and the predominant negative-ion species changes from CO ₃ ^– to NO ₂ ^– , a decrease ink _d occurs destabilizing the discharge. Since NO ₂ ^– and NO ₃ ^– are largely unreactive with respect to associative detachment,k _d depends in a sensitive fashion on the concentration of certain minority negative ions (O^–, O ₂ ^– ) and neutrals (CO, O, N). The sufficient conditions for the dissociative-attachment instability are much less sensitive to changes in the electron-ion and ion-ion recombination rate coefficients resulting from the ion aging process.     

Magnetoacoustic Oscillations of a Plasma Containing Two Species of Ions

Numerical calculations of linear magnetoacoustic resonant phenomena in a plasma containing two species of ions have been made for a cylindrical plasma with a model which includes the effects of collisional damping and radial non-uniformities in temperature and number density. At sufficiently high temperatures two frequencies are predicted at which magnetoacoustic resonances for the first radial mode will occur. These are expected from considerations of the effects of the ion-ion hybrid resonance.     

Thermodynamic characteristics of a metastable plasma

The equation of state is obtained for an ion-ion plasma which is stable with respect to recombination processes. The regions of thermodynamic stability of a nonideal plasma and of mixtures of such a plasma with an ideal plasma are determined by considering isotherms. It is shown that such a plasma-gas mixture possesses elastic properties.General Physics Institute, Russian Academy of Sciences, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 8–14, January, 1993.     

The absorptive part of the nucleus-nucleus potential in a semiclassical approach

The imaginary part of the optical potential for nuclear ion-ion scattering in the energy range 20 MeV ?E/A ? 200 MeV is derived using Feshbach's projection formalism. It is defined as the effective absorptive potential in the projected one-body Schroedinger equation for the relative motion of the colliding nuclei. Calculations are done in the Thomas-Fermi approximation, which accounts in a simple way for all phase-space effects as well as for the finite size of the ions. Intrinsic excitations are considered to be of one particle — one hole type in either of the ions, the other remaining in its ground state. The effective two-body interaction is taken to be of finite range. Further simplifications of the model consist in neglecting antisymmetrization between the mutual wave functions of the two ions and in the omission of the Coulomb energy.     

Statistical mechanics of “atoms” in hot,partially ionized matter: The theory of the one electron green function

We have considered the problem of calculating the one electron Green function for hot, partially ionized condensed matter as a means of computing the statistical thermodynamics and transport properties of the system. Abandoning the Wigner-Seitz sphere and using instead the correlation sphere defined by the ion-ion correlation length of the system we define a reference model for calculating the Hartree-Fock (H-F) states of the system. No ion microfields are needed. The reference model naturally gives rise to a static ion-micropotential. This, plus the electron H-F Hamiltonian is diagonalized to give the solutions of the reference model. Next, we consider the corrections to the energy levels arising from the dynamically screened charge density fluctuations of the system with its bound and free electrons, ions, and also taking into account the effect of the non-uniform distributions prevailing within the correlation sphere. By identifying response function like components in the mass operator and replacing them by their hydrodynamic approximations the screened 2nd order mass operator is obtained in a very tractable form. This 2nd order mass operator could be converted to an all-order form using a non-linear ion-electron pseudopotential V_ie. The construction of V_ie and the effective non-linear ion-ion potential V_i?i needed for calculating the ion-ion structure factor are considered. The effect of the inhomogeneities is brought in through these structure factors S(q, Q) which enter naturally into the theory. The final expressions provide, for example, an explicit formula for the correlation effects arising from ion dynamics and contributing to the position and width of the electronic levels of an “atom” immersed in a plasma.     

Secondary ion mass spectra of alkali halides

Mass spectra of positive and negative secondary ions from various alkali halides have been measured in the Manitoba time-of-flight mass spectrometer. The ions were produced by Cs⁺ and K⁺ bombardment at primary ion energies of 3 to 19 keV for the positive spectra, and 11 to 28 keV for the negative spectra. The ions measured were those emitted within a time interval ～ 20 ns after the primary ion impact. The secondary ion yields are strongly dependent on the sample composition and treatment; prior irradiation may change the yield by an order of magnitude or more. The secondary ion yields also depend strongly on the energy loss of the primary ion, but the ratio of yields of different cluster ions from a given target is almost independent of this parameter. The results appear to be consistent with models in which the clusters are ejected directly from the target, but do not determine whether or not they possess the original surface structure. The results may also be described by a recombination model if the recombination is essentially complete.     

Double resonant charge exchange in ion-ion collisions

The process of resonant double charge exchange in low energy ion-ion collisions is considered. The effects of the Coulomb interaction of the nuclei are taken into account. Cross section calculations are performed both for completely and partially stripped projectile ions with 3? Z ? 10.     

Possible use of recombination for selective effects on the populations of excited atomic and ionic levels. I

Studies of recombination in a plasma of moderate density are reviewed. Conclusions are drawn regarding the possible use of ternary recombination to produce elevated populations of high-lying excited atomic and ionic levels and regarding the conditions in a gas-discharge plasma which provide the sharpest differences among these populations, with the higher-lying levels populated predominantly. There are additional recombination processes which could produce elevated populations in certain cases in the high-lying excited levels of atoms and ions haying displaced levels: radiationless two-particle recombination and ternary recombination of ions formed by the stripping of an electron from an inner shell.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 3, pp. 104–111, March, 1971.