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Gases and solids
Classified abstracts 353-494 Classified abstracts 353--363 on this page
Editor's note
The label immediately following the title of each item denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).
I. General v a c u u m science and engineering 10. VACUUM SCIENCE AND TECHNOLOGY 10:64 353. Conference on high vacuum physics and technology. (Czechoslovakia) A report is given on the Conference that was held in June 1967 in Dresden, East Germany. P Repa, Czech J Phys, AI7 (6), 1967, 616-617 (in Czech). 10 : 16 354. Principles of vacuum technology. Part 2. (Czechoslovakia) The fundamental concepts involved in sorption-desorption phenomena are briefly described. The practical implications of these concepts and the significance of the term "pumping speed" in this connection, are discussed. L Paty, Jemna Mech Opt, 12 (11), Nov 1967, 353-355 (in Czech). 14. KINETIC THEORY OF GASES 14 355. On the kinetic theory of partially ionized gases. (USA) An approach for evaluating the thirteen moments of the Boltzmann collision integral for electron-ion and electron-neutral collisions in an ionized gas is developed which utilizes the smallness of the electron-mass, and is different from other previous approaches. J T Yen, Rep RE-289, June 1967, 30 pages (Sci Tech Aerospace Reps, 5 (17), 3135, N67-31132). 14 356. Calculation of processes of evacuation of a gas volume. (USSR) A calculation method for the evacuation process of a gas volume is proposed. It is based on application of thermodynamic equations for variable mass bodies and assumptions of temperature constancy of internal surface of the volume and transfer of heat from the surface to the gas by free convection. N P Belik et al, Rep FTD-MT-65-329; TT-67-61680; AD-651090, March 1967, 8 pages (Sci Tech Aerospace Reps, 5 (18), 3355, N6732282). 15. FLUID DYNAMICS 15 357. Fundamental solution of the linear Boitzmann equation. (USA) The fundamental solution of the time-independent linear Boltzmann equation is presented. The physical significance of the fundamental solution is the perturbed field in the steady rarefied gas flow over a point source. Provision of the fundamental solution permits the construction of a solution of the boundary-value problem in a uniform rarefied gas flow past a body. In nearly free-molecular flow of large Knudsen number, the fundamental solution describes the actual flow field which has essentially three different flow regimes: free-molecular near the body; far away from the body the flow may be described fluid-dynamically in terms of density, velocity and temperature; and at distances of the order of one mean free path, a transition region. E-Y Yu, Phys Fluids, 10 (11), Nov 1967, 2466-2474. 15 358. The Boltzmann equation with cutoff potentials. (USA) After showing that the existence of a cutoff in the two-body interaction follows from consistency in the frame of assumptions upon which the Boltzmann equation is based, the collision operators for such cutoff potentials are studied in detail. It is shown that the essential properties required to build a rigorous mathematical theory of the linearized Boltzmann equation are possessed by the collision with
cutoff potentials. In particular, results of basic importance for existence, uniqueness and approach to equilibrium are proved. C Cercignani, Phys Fluids, 10 (10), Oct 1967, 2097-2104. 15 359. Simplified expressions for the transport properties of ionized monoatomic gases. (USA) Simplified theoretical expressions for the transport properties of ionized gas mixtures are derived within the framework of the Chapman-Enskog-Burnett method. The properties of equilibrium partially ionized argon are then computed with these expressions and compared with values obtained with the exact theory. Agreement was found to be satisfactory. R S Devoto, Phys Fluids, 10 (10), Oct 1967, 2105-2112. 15 360. Source-flow expansion of a partially ionized gas into a vacuum. (USA) Some theoretical results are presented for use in the prediction of flow conditions in free-jet plasma expansions. The model investigated is a one-dimensional, spherically symmetric, supersonic source flow of partially ionized argon, under the assumption that this model represents a reasonably good approximation to the centre-line flow conditions of a free-jet. Two-body ionization and collisional-radiative recombination are the reactions considered. Two types of source flow are investigated: a simple supersonic source flow with the initial supersonic state assumed to be an equilibrium one; and a nozzle expansion from an equilibrium stagnation state to slightly supersonic conditions, followed by source flow. Y S Chou and L Talbot, Am Inst Aeronautics and Astronautics J, 5 (12), Dec 1967, 2t66-2172. I
16. GASES AND SOLIDS 16 : 10 Principles of vacuum technology. Part 2. See abstract number 354. 16 361. The trapping of low-energy noble gas ions at a tungsten surface. (Great Britain) Experimental results for the variation with energy below 1 keV of the trapping efficiency for noble gas ions incident upon atomically clean polycrystalline tungsten are discussed and compared. A theory is developed enabling a value of the trapping efficiency to be calculated using the repulsive interaction potentials. The curves derived from this theory show good agreement with the experimental curves for the gas-metal combinations He-W, Ne-W, Ar-W and Kr-W. K J Close and J Yarwood, BritJApplPhys, 18 (11), 1967, 1593-1598. 16:63 362. Literature search of physical property data and of composite surface work function models. (USA) Five experimental techniques for obtaining surface physical property data are described and include low energy diffraction, flash filament electron impact desorption, work function changes due to adsorbed gas, and adsorption site densities. The data are listed alphabetically according to substrate. L W Swanson et al, Rep NASA-CR-85562, Dec 1966, 132 pages (Sci Tech Aerospace Reps, 5 (17), 3148, N-67-30836). 16 363. Investigation of water chemisorption on the tungsten surface.
(USSR) Polycrystalline tungsten wire at a temperature of 300°K was exposed to water vapour pressures of 3 × 10 8 torr and then the water was desorbed by the flash method in a time-of-flight mass spectrometer. Three phases of the chernisorption were observed. In two of them water is dissociated to H ÷ OH with easy desorption of H. Hydroxyl
189
Editor's note
The label immediately following the title of each item denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).
I. General v a c u u m science and engineering 10. VACUUM SCIENCE AND TECHNOLOGY 10:64 353. Conference on high vacuum physics and technology. (Czechoslovakia) A report is given on the Conference that was held in June 1967 in Dresden, East Germany. P Repa, Czech J Phys, AI7 (6), 1967, 616-617 (in Czech). 10 : 16 354. Principles of vacuum technology. Part 2. (Czechoslovakia) The fundamental concepts involved in sorption-desorption phenomena are briefly described. The practical implications of these concepts and the significance of the term "pumping speed" in this connection, are discussed. L Paty, Jemna Mech Opt, 12 (11), Nov 1967, 353-355 (in Czech). 14. KINETIC THEORY OF GASES 14 355. On the kinetic theory of partially ionized gases. (USA) An approach for evaluating the thirteen moments of the Boltzmann collision integral for electron-ion and electron-neutral collisions in an ionized gas is developed which utilizes the smallness of the electron-mass, and is different from other previous approaches. J T Yen, Rep RE-289, June 1967, 30 pages (Sci Tech Aerospace Reps, 5 (17), 3135, N67-31132). 14 356. Calculation of processes of evacuation of a gas volume. (USSR) A calculation method for the evacuation process of a gas volume is proposed. It is based on application of thermodynamic equations for variable mass bodies and assumptions of temperature constancy of internal surface of the volume and transfer of heat from the surface to the gas by free convection. N P Belik et al, Rep FTD-MT-65-329; TT-67-61680; AD-651090, March 1967, 8 pages (Sci Tech Aerospace Reps, 5 (18), 3355, N6732282). 15. FLUID DYNAMICS 15 357. Fundamental solution of the linear Boitzmann equation. (USA) The fundamental solution of the time-independent linear Boltzmann equation is presented. The physical significance of the fundamental solution is the perturbed field in the steady rarefied gas flow over a point source. Provision of the fundamental solution permits the construction of a solution of the boundary-value problem in a uniform rarefied gas flow past a body. In nearly free-molecular flow of large Knudsen number, the fundamental solution describes the actual flow field which has essentially three different flow regimes: free-molecular near the body; far away from the body the flow may be described fluid-dynamically in terms of density, velocity and temperature; and at distances of the order of one mean free path, a transition region. E-Y Yu, Phys Fluids, 10 (11), Nov 1967, 2466-2474. 15 358. The Boltzmann equation with cutoff potentials. (USA) After showing that the existence of a cutoff in the two-body interaction follows from consistency in the frame of assumptions upon which the Boltzmann equation is based, the collision operators for such cutoff potentials are studied in detail. It is shown that the essential properties required to build a rigorous mathematical theory of the linearized Boltzmann equation are possessed by the collision with
cutoff potentials. In particular, results of basic importance for existence, uniqueness and approach to equilibrium are proved. C Cercignani, Phys Fluids, 10 (10), Oct 1967, 2097-2104. 15 359. Simplified expressions for the transport properties of ionized monoatomic gases. (USA) Simplified theoretical expressions for the transport properties of ionized gas mixtures are derived within the framework of the Chapman-Enskog-Burnett method. The properties of equilibrium partially ionized argon are then computed with these expressions and compared with values obtained with the exact theory. Agreement was found to be satisfactory. R S Devoto, Phys Fluids, 10 (10), Oct 1967, 2105-2112. 15 360. Source-flow expansion of a partially ionized gas into a vacuum. (USA) Some theoretical results are presented for use in the prediction of flow conditions in free-jet plasma expansions. The model investigated is a one-dimensional, spherically symmetric, supersonic source flow of partially ionized argon, under the assumption that this model represents a reasonably good approximation to the centre-line flow conditions of a free-jet. Two-body ionization and collisional-radiative recombination are the reactions considered. Two types of source flow are investigated: a simple supersonic source flow with the initial supersonic state assumed to be an equilibrium one; and a nozzle expansion from an equilibrium stagnation state to slightly supersonic conditions, followed by source flow. Y S Chou and L Talbot, Am Inst Aeronautics and Astronautics J, 5 (12), Dec 1967, 2t66-2172. I
16. GASES AND SOLIDS 16 : 10 Principles of vacuum technology. Part 2. See abstract number 354. 16 361. The trapping of low-energy noble gas ions at a tungsten surface. (Great Britain) Experimental results for the variation with energy below 1 keV of the trapping efficiency for noble gas ions incident upon atomically clean polycrystalline tungsten are discussed and compared. A theory is developed enabling a value of the trapping efficiency to be calculated using the repulsive interaction potentials. The curves derived from this theory show good agreement with the experimental curves for the gas-metal combinations He-W, Ne-W, Ar-W and Kr-W. K J Close and J Yarwood, BritJApplPhys, 18 (11), 1967, 1593-1598. 16:63 362. Literature search of physical property data and of composite surface work function models. (USA) Five experimental techniques for obtaining surface physical property data are described and include low energy diffraction, flash filament electron impact desorption, work function changes due to adsorbed gas, and adsorption site densities. The data are listed alphabetically according to substrate. L W Swanson et al, Rep NASA-CR-85562, Dec 1966, 132 pages (Sci Tech Aerospace Reps, 5 (17), 3148, N-67-30836). 16 363. Investigation of water chemisorption on the tungsten surface.
(USSR) Polycrystalline tungsten wire at a temperature of 300°K was exposed to water vapour pressures of 3 × 10 8 torr and then the water was desorbed by the flash method in a time-of-flight mass spectrometer. Three phases of the chernisorption were observed. In two of them water is dissociated to H ÷ OH with easy desorption of H. Hydroxyl
189