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468. Condensation of hydrogen on tungsten
Classified abstracts 464-614 Classified abstracts 464-471 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 s c i e n c e and e n g i n e e r i n g 14. KINETIC THEORY OF GASES 14 464. Reactions of metastable nitrogen atoms. (USA) The line absorption technique was applied to the kinetic theory of the two metastable states (atomic nitrogen) N(22D) and N(22p) in a flowing afterglow system. The optical absorption of the N1 1493 A ° (2p32D-3s2P) and 1743 A (2p32P-3s2P) transitions were used for the quantitative measurement of N(2=D) and N(22P) concentrations. Deactivation of N(2D) and N(2p) by the Pyrex tube wall was found to be very efficient, i.e., occurs at nearly every collision. The secondorder rate constants at 300°K for the removal of N(ZD) by O2, N20, CO2, NO, N=, Ar and He are listed. It was found that the process for the first four reactant gases results in chemical reaction rather than physical quenching. C-L Lin and F Kaufman, J Chem Phys, 55 (8), 15th Oct 1971, 37603769. 14 465. Measuring the temperature of a rarefied medium using atomic beam scattering. (USSR) In the investigation of rarefied hot gases or plasma it is necessary to measure the temperature and velocity of the directed beams and to determine the velocity distribution function of the particles. For determination of the velocity distribution function of atoms of gas or ions of plasma, it is proposed to inject a monokinetic beam of atomic particles into the investigated gas and to measure the velocity distribution of the particles of the beam scattered to some fixed angle by collisions with particles of the medium. It is shown that the distribution of scattered particles of the beam reflects the distribution of particles of the medium along the determined direction in space, which is given by the directions of the injected beam and the scattered particles. The method enables anisotropy in the distribution of particles of the medium to be investigated. Temperatures of rarefied helium were determined in a tungsten furnace in the range 800 to 2300°K with scattering of D + ions with energy from 2.5 to 12 keV. V G Abramov et al, Zh Tekh Fiz, 41 (9), Sept 1971, 1924-1932 (in
Russian). 14 466. Utilization of scattering with boundary angle for determination of temperature of rarefied medium. (USSR) A method of temperature measurement for rarefied gas or plasma is presented, which is based on atomic beam scattering of particles with mass higher than that of the atomic particles of the medium. It is shown that measurement of the intensity of scattered particles at an angle smaller than the boundary angle (given by the ratio of the mass of injected particles to the mass of particles of the medium), enables one to determine the particle density of the medium and, at angles higher than the boundary angle, it enables one to determine the temperature of the medium. The differential cross section of scattering of ions of helium He +2 on protons at different ratios of proton temperature and helium ion energy, is presented. The method is not limited on the high temperature side. V V Afrosimov and A I Kislyakov, Zh Tekh Fiz, 41 (9), Sept 1971, 1933-1935 (in Russian).
canal in the discharge of an argon ion laser is considered. A formula is obtained which gives the dependence of the pressure difference between the anode and cathode bulbs on the dimensions of the capillary and the encircling canal. It is found that the pressure of neutral atoms increases from the cathode to the anode. The pressure of neutral atoms is constant and equal to the cathode pressure almost along the whole length of the capillary with exception of its anode end. The calculated dependences are compared with the experimental data on the pressure difference between anode and cathode bulbs and a good agreement is found. It is concluded that the pressure in the cathode bulb and not the filling pressure forms the basic characteristic of the considered discharge. The filling pressure can be several times higher than the pressure of neutral atoms in the capillary. B G Freykman, Zh Tekh Fiz, 41 (10), Oct 1971, 2211-2215 (in Russian). 16. GASES AND SOLIDS 16 468. Condensation of hydrogen on tungsten. (USA) The condensation kinetics of hydrogen on the (110), (111) and (100) planes of tungsten are examined as functions of crystal temperature, coverage and population of the various bonding states. Measurements were carried out simultaneously on all three crystals in the same ultrahigh vacuum system in order to accurately compare sticking coefficients and amounts adsorbed. There are large variations in the initial sticking coefficients So. This implies that the electron transition involved in bond formation depends sensitively on the geometric and electronic structures of the substrates. Models are developed and these are compared with the experimental results. P W Tamm and L D Schmidt, J Chem Phys, 55 (9), I st Nov 1971, 42534259. 16 469. Adsorption of oxygen and water vapour on chemically treated germanium single crystal surfaces. 4. On the kinetics of water adsorption. (Hungary) Binding of water vapour on chemically treated germanium single crystal surfaces is a slow process requiring several hours to reach adsorption equilibrium. Changes in the quantity of adsorbed water versus time were studied by means of the tritium indication method. It was found that water vapour is bound by weak chemisorption and germanium atoms of different degrees of oxidation occupying some sterically favourable sites in the germanium dioxide act as adsorption centres. Diffusion can proceed only very slowly and is hindered both by adsorption and by steric conditions. J Gibber et al, Kemiai Kozlemenyek, 35 (2), 1971, 161-169 (in Hun-
garian). 16 470. Adsorption of oxygen and water vapour on chemically treated germanium single crystal surfaces. 3. Isotherms and their evaluation. (Hungary) A volumetric method was used for the study of the sorption of oxygen and of the oxygen-water vapour mixture as well as for the plotting of the water vapour isotherms at 16°C both on germanium samples and on germanium dioxide powders. Tritium indication was applied to the measurement of water vapour adsorption in pure nitrogen and air at different germanium surface temperatures. d Gibber ct al, Kemiai Kozlemenyek, 35 (2), 1971, 149-160 (in Hun-
15. FLUID DYNAMICS
garian).
15 467. Distribution of the pressure of neutral atoms along the length of the discharge tube of ion laser. (USSR) On the basis of a semi-empirical description of gas flow in the transition regime, circulation of gas along the capillary and the encircling
16 471. Influence of oxygen pressure on early stages of molybdenum oxidation. (USSR) Influence of oxygen pressure on early stages of molybdenum oxidation is investigated by secondary ion-ion emission method. A molyb-
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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 s c i e n c e and e n g i n e e r i n g 14. KINETIC THEORY OF GASES 14 464. Reactions of metastable nitrogen atoms. (USA) The line absorption technique was applied to the kinetic theory of the two metastable states (atomic nitrogen) N(22D) and N(22p) in a flowing afterglow system. The optical absorption of the N1 1493 A ° (2p32D-3s2P) and 1743 A (2p32P-3s2P) transitions were used for the quantitative measurement of N(2=D) and N(22P) concentrations. Deactivation of N(2D) and N(2p) by the Pyrex tube wall was found to be very efficient, i.e., occurs at nearly every collision. The secondorder rate constants at 300°K for the removal of N(ZD) by O2, N20, CO2, NO, N=, Ar and He are listed. It was found that the process for the first four reactant gases results in chemical reaction rather than physical quenching. C-L Lin and F Kaufman, J Chem Phys, 55 (8), 15th Oct 1971, 37603769. 14 465. Measuring the temperature of a rarefied medium using atomic beam scattering. (USSR) In the investigation of rarefied hot gases or plasma it is necessary to measure the temperature and velocity of the directed beams and to determine the velocity distribution function of the particles. For determination of the velocity distribution function of atoms of gas or ions of plasma, it is proposed to inject a monokinetic beam of atomic particles into the investigated gas and to measure the velocity distribution of the particles of the beam scattered to some fixed angle by collisions with particles of the medium. It is shown that the distribution of scattered particles of the beam reflects the distribution of particles of the medium along the determined direction in space, which is given by the directions of the injected beam and the scattered particles. The method enables anisotropy in the distribution of particles of the medium to be investigated. Temperatures of rarefied helium were determined in a tungsten furnace in the range 800 to 2300°K with scattering of D + ions with energy from 2.5 to 12 keV. V G Abramov et al, Zh Tekh Fiz, 41 (9), Sept 1971, 1924-1932 (in
Russian). 14 466. Utilization of scattering with boundary angle for determination of temperature of rarefied medium. (USSR) A method of temperature measurement for rarefied gas or plasma is presented, which is based on atomic beam scattering of particles with mass higher than that of the atomic particles of the medium. It is shown that measurement of the intensity of scattered particles at an angle smaller than the boundary angle (given by the ratio of the mass of injected particles to the mass of particles of the medium), enables one to determine the particle density of the medium and, at angles higher than the boundary angle, it enables one to determine the temperature of the medium. The differential cross section of scattering of ions of helium He +2 on protons at different ratios of proton temperature and helium ion energy, is presented. The method is not limited on the high temperature side. V V Afrosimov and A I Kislyakov, Zh Tekh Fiz, 41 (9), Sept 1971, 1933-1935 (in Russian).
canal in the discharge of an argon ion laser is considered. A formula is obtained which gives the dependence of the pressure difference between the anode and cathode bulbs on the dimensions of the capillary and the encircling canal. It is found that the pressure of neutral atoms increases from the cathode to the anode. The pressure of neutral atoms is constant and equal to the cathode pressure almost along the whole length of the capillary with exception of its anode end. The calculated dependences are compared with the experimental data on the pressure difference between anode and cathode bulbs and a good agreement is found. It is concluded that the pressure in the cathode bulb and not the filling pressure forms the basic characteristic of the considered discharge. The filling pressure can be several times higher than the pressure of neutral atoms in the capillary. B G Freykman, Zh Tekh Fiz, 41 (10), Oct 1971, 2211-2215 (in Russian). 16. GASES AND SOLIDS 16 468. Condensation of hydrogen on tungsten. (USA) The condensation kinetics of hydrogen on the (110), (111) and (100) planes of tungsten are examined as functions of crystal temperature, coverage and population of the various bonding states. Measurements were carried out simultaneously on all three crystals in the same ultrahigh vacuum system in order to accurately compare sticking coefficients and amounts adsorbed. There are large variations in the initial sticking coefficients So. This implies that the electron transition involved in bond formation depends sensitively on the geometric and electronic structures of the substrates. Models are developed and these are compared with the experimental results. P W Tamm and L D Schmidt, J Chem Phys, 55 (9), I st Nov 1971, 42534259. 16 469. Adsorption of oxygen and water vapour on chemically treated germanium single crystal surfaces. 4. On the kinetics of water adsorption. (Hungary) Binding of water vapour on chemically treated germanium single crystal surfaces is a slow process requiring several hours to reach adsorption equilibrium. Changes in the quantity of adsorbed water versus time were studied by means of the tritium indication method. It was found that water vapour is bound by weak chemisorption and germanium atoms of different degrees of oxidation occupying some sterically favourable sites in the germanium dioxide act as adsorption centres. Diffusion can proceed only very slowly and is hindered both by adsorption and by steric conditions. J Gibber et al, Kemiai Kozlemenyek, 35 (2), 1971, 161-169 (in Hun-
garian). 16 470. Adsorption of oxygen and water vapour on chemically treated germanium single crystal surfaces. 3. Isotherms and their evaluation. (Hungary) A volumetric method was used for the study of the sorption of oxygen and of the oxygen-water vapour mixture as well as for the plotting of the water vapour isotherms at 16°C both on germanium samples and on germanium dioxide powders. Tritium indication was applied to the measurement of water vapour adsorption in pure nitrogen and air at different germanium surface temperatures. d Gibber ct al, Kemiai Kozlemenyek, 35 (2), 1971, 149-160 (in Hun-
15. FLUID DYNAMICS
garian).
15 467. Distribution of the pressure of neutral atoms along the length of the discharge tube of ion laser. (USSR) On the basis of a semi-empirical description of gas flow in the transition regime, circulation of gas along the capillary and the encircling
16 471. Influence of oxygen pressure on early stages of molybdenum oxidation. (USSR) Influence of oxygen pressure on early stages of molybdenum oxidation is investigated by secondary ion-ion emission method. A molyb-
161