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Theory of current characteristics of a thin dielectric film under slow electron impact
Classified abstracts
223-232
discussed. Scattering distributions of monatomic and diatomic gases from clean and CO covered Pt single crystal surfaces indicate efficient translational vibrational (T,-I’,) energy transfer when the surface is CO covered. The efficient energy transfer is attributed to low frequency bending modes of the CO molecules on the surface that absorb the incident particle energy. S L Bemasek and G A Somorjai, J Chem Phys, 60 (ll), 1974, 4552-4556. 40 223. Gas-phase reaction of Ba with N20. II. Mechanism of reaction. (USA) A reaction mechanism and a correlation diagram argument are presented to account for the high photon yield of the chemiluminescent reaction of Ba atoms with NzO. The arguments suggests that reactions of alkaline earth atoms with N20 and with 0, may be suitable for electronic-transition chemical lasers. R W Field et al, J Chem Phys, 60 (ll), 1974, 43774382. 40 224. Gas-phase reaction of Ba with NZO. I. Measurement of production efficiency of excited states. (USA) Quantitative spectroscopic measurements were made on chemiluminescence resulting from reactions of barium atoms with oxidant molecules. Reactions occur with small partial pressures of reactants in a flow of inert carrier gas, usually argon, helium or nitrogen, at pressures in the Torr range. The yield for BaO A-X photons is strongly dependent on inert-gas pressure and is measured to be 20% at pressures near 10 torr. A kinetic scheme accounting for gross features of the observations is presented. C R Jones and H P Broida, J Chem Phys, 60 (ll), 1974, 43694376. 40 225. Electron-impact excitation of the %SO and %I0states of atomic oxygen. (USA) The apparatus used has been described previously and a reference is given. Improvements are discussed. Absolute cross sections for the excitation-of the 01 ‘S (%“) and 3S (%‘) states by electron energies from threshold to 300 eV. The %” cross section is 5.3 x lo-i7 cm2 * 40 o/0at its peak at 20 eV. The ‘Sa cross section has a maximum value of 2.5 x 10-l’ cm2 *50°% at 15 eV. Both cross sections are larger than values predicted by theory. E J Stone and E C Zipf, J Chem Phys, 60 (1 l), 1974,4237-4242. 41. METALS AND ALLOYS 41 226. Secondary electron emission from platinum-black-coated surf&es. (GB) Platinum black is shown to be capable of withstanding elevated temperatures whilst maintaining low secondary yield values. Auger and energy loss spectra from its surface are reported. (GB) B Wright and E B Pattlaon, J Phys D: Appl Phys, 7, (ll), 1974, 1560-1565. 41 227. Material for parts of electrical vacuum apparatus. (USSR) The low ductility of the molybdenum alloy frequently used in parts of electrical vacuum equipment working at over 1000°C causes premature failures, while the addition of a high proportion of rhenium to the molybdenum increases ductility at the expense of heat resistance. In the improved material here proposed a powder mixture is first prepared containing 50-89.4x Mb and 10-49.5 % Re toaether with traces CUD to 0.3x) of K20 and SiO,. This material is processed by conveniional methods of-powder metallurgy (moulding and sinterlng at 2000-2300°C). The resultant blocks may readily be worked into wire 20 pm in diameter, using techniques similar to those employed for tungsten. The additives greatly increase the heat resistance of the alloys. The strength of a 100 pm wire containing 20% Re annealed at 600°C is 95 kg/mm2 and its.relative elongation at rupture 25%. V M Arnosov et al, Soviet Patent class H 01 i, l/48, No. 387454 claimed 21st June 1971, publd 13th Nov 1973 (in Russian). 41 228. Mass spectrometric study of gas-phase clustering reactions: Hydration of the monovalent bismuth ion. (USA) Gas-phase hydration equilibria of the monovalent bismuth ion were investigated over the temperature range 10~160°C using highpressure mass spectrometry. The hydration enthalpies and entropies 90
for the clusters, Bi+ (H,O),, n 2 6, were derived from appropriate van’t Hoff plots. A comparison of the stability of bismuth-ion hydrates reveals further evidence of chemical bonding in these heavy metal-ion clusters. Although the basic apparatus has been previously described (to which reference is made) a number of changes were made. All metal components were used to obtain better outgassing. Also, a IO-in. oil diffusion pump was used instead of the original 4-in. pump. This allowed the reaction cell to be operated at higher pressures than previously while maintaining a pressure of 5 x 10e6 torr or less in the vacuum chamber. I N Tang and A W Castleman, J Chem Phys, 60 (lo), 1974,3981-3986. 41 229. Large angle inelastic scattering of Na+ by D2. (USA) Results are reported for large angle scattering of Na+ by Dz, HD and H, in the initial relative energy range of 0.74-16.9 eV. It is concluded that perpendicular (C,,)ratherthan collinear conformations of the Na+-D2 system produce the most intense inelastic scattering. Results are given for exact classical trajectory calculations. The apparatus consisted of an ion source, a cell and a detection system. These were mounted on the lid of a IO-in. stainless vacuum can. The system was pumped by a 6-in. oil diffusion pump protected by a liquid nitrogen cooled baffle, and was baked at 125°C for 12 h prior to experiments. Operating pressures were less than lo-’ torr. W L Dimpfl and B H Mahan, J Chem Phys, 60 (8), 1974, 3238-3250. 41 230. Molecular beam study of the K-CF,I reaction: Detailed differential reaction cross section and energy disposal. (USA) The reaction of a velocity-selected K beam with a crossed beam of CFBI (from a thermal capillary-array source) was studied by the velocity-analysis technique. The KI product flux was transformed to yield the center-of-mass (cm) detailed differential reactions cross section. The cm cross section is “backward” peaked, but there is a substantial reactive contribution in the forward hemisphere as well. The average released into translational recoil of the products is only 8.5 kcal/mole, so that some 70% of the total available energy is partitioned into internal degrees of freedom of the products. The basic apparatus has been previously described and suitable references are given. AG A M Rulis et al, J Chem Phys, 60 (7), 1974, 2822-2827. 41 231. Theory of current characteristics of a thin dielectric film under slow electron impact. A relation between the current transmitted by a thin dielectric film as a function of incident electron energy and the electronic energy structure of the film is derived. These current characteristics have been measured by W H Hamill et al (References given). For low energies, l-4 eV, it is found that the current characteristics are insensitive to the detailed energy structure of the solid. In the moderately high energy range 4-10 eV, the transmitted current is more sensitive to the energy levels of the solid, but the relation is not straight-forward, involving a convolution of a joint density of states and a conduction band density of states. M E Harrigan, J Chem Phys, 60 (12), 1974, 49094919. 42. GLASS, CERAMICS AND REFRACTORY
OXIDES
42~23 232. Method of manuthcturing an insulator. (USSR) A vacuum-tight insulator based on vacuum-melted stainless steel is described. Art enamel of the following composition is deposited on the steel: SiO, 61.8-65.8. Al,O, 6.6-7.5. B20, 2.2-3.7. CaO 4.9-5.5. BaO 6.5-9.6; MnO 2.6-3.3, Na,O 317-4.5, K20 3.0-4.5, Li2d 0.5-1.0, MOO* 0.14.2 wt. %; this is then roasted at lOOO-1OlO’C. A slightly different enamel is then deposited: SiOl 58.7-61.4, A1,03 4.6-5.8, B203 0.9-2.4, CaO 3.8-4.8, NazO 17.5-18.4, K20 0.6-1.6, TiOl 7.1-8.2, Co203 0.8-1.3, Moo9 0.6-0.7; this is roasted at 84&85o”C. The enamels are prepared by wet-milling the components in a ball mill, diluted with distilled water to the desired viscosity, and left standing for 24 h. Before application the metal surface is sandblasted and degreased. After heat treatment the enamel is allowed to cool with the furnace; its total thickness is 500 pm. I P Chelpanov et al, Soviet Patent, class H 01 b, 17126, C 03 c, 7100, No. 375686, claimed 10th March 1970, publd 11th May 1973 (in Russian).
223-232
discussed. Scattering distributions of monatomic and diatomic gases from clean and CO covered Pt single crystal surfaces indicate efficient translational vibrational (T,-I’,) energy transfer when the surface is CO covered. The efficient energy transfer is attributed to low frequency bending modes of the CO molecules on the surface that absorb the incident particle energy. S L Bemasek and G A Somorjai, J Chem Phys, 60 (ll), 1974, 4552-4556. 40 223. Gas-phase reaction of Ba with N20. II. Mechanism of reaction. (USA) A reaction mechanism and a correlation diagram argument are presented to account for the high photon yield of the chemiluminescent reaction of Ba atoms with NzO. The arguments suggests that reactions of alkaline earth atoms with N20 and with 0, may be suitable for electronic-transition chemical lasers. R W Field et al, J Chem Phys, 60 (ll), 1974, 43774382. 40 224. Gas-phase reaction of Ba with NZO. I. Measurement of production efficiency of excited states. (USA) Quantitative spectroscopic measurements were made on chemiluminescence resulting from reactions of barium atoms with oxidant molecules. Reactions occur with small partial pressures of reactants in a flow of inert carrier gas, usually argon, helium or nitrogen, at pressures in the Torr range. The yield for BaO A-X photons is strongly dependent on inert-gas pressure and is measured to be 20% at pressures near 10 torr. A kinetic scheme accounting for gross features of the observations is presented. C R Jones and H P Broida, J Chem Phys, 60 (ll), 1974, 43694376. 40 225. Electron-impact excitation of the %SO and %I0states of atomic oxygen. (USA) The apparatus used has been described previously and a reference is given. Improvements are discussed. Absolute cross sections for the excitation-of the 01 ‘S (%“) and 3S (%‘) states by electron energies from threshold to 300 eV. The %” cross section is 5.3 x lo-i7 cm2 * 40 o/0at its peak at 20 eV. The ‘Sa cross section has a maximum value of 2.5 x 10-l’ cm2 *50°% at 15 eV. Both cross sections are larger than values predicted by theory. E J Stone and E C Zipf, J Chem Phys, 60 (1 l), 1974,4237-4242. 41. METALS AND ALLOYS 41 226. Secondary electron emission from platinum-black-coated surf&es. (GB) Platinum black is shown to be capable of withstanding elevated temperatures whilst maintaining low secondary yield values. Auger and energy loss spectra from its surface are reported. (GB) B Wright and E B Pattlaon, J Phys D: Appl Phys, 7, (ll), 1974, 1560-1565. 41 227. Material for parts of electrical vacuum apparatus. (USSR) The low ductility of the molybdenum alloy frequently used in parts of electrical vacuum equipment working at over 1000°C causes premature failures, while the addition of a high proportion of rhenium to the molybdenum increases ductility at the expense of heat resistance. In the improved material here proposed a powder mixture is first prepared containing 50-89.4x Mb and 10-49.5 % Re toaether with traces CUD to 0.3x) of K20 and SiO,. This material is processed by conveniional methods of-powder metallurgy (moulding and sinterlng at 2000-2300°C). The resultant blocks may readily be worked into wire 20 pm in diameter, using techniques similar to those employed for tungsten. The additives greatly increase the heat resistance of the alloys. The strength of a 100 pm wire containing 20% Re annealed at 600°C is 95 kg/mm2 and its.relative elongation at rupture 25%. V M Arnosov et al, Soviet Patent class H 01 i, l/48, No. 387454 claimed 21st June 1971, publd 13th Nov 1973 (in Russian). 41 228. Mass spectrometric study of gas-phase clustering reactions: Hydration of the monovalent bismuth ion. (USA) Gas-phase hydration equilibria of the monovalent bismuth ion were investigated over the temperature range 10~160°C using highpressure mass spectrometry. The hydration enthalpies and entropies 90
for the clusters, Bi+ (H,O),, n 2 6, were derived from appropriate van’t Hoff plots. A comparison of the stability of bismuth-ion hydrates reveals further evidence of chemical bonding in these heavy metal-ion clusters. Although the basic apparatus has been previously described (to which reference is made) a number of changes were made. All metal components were used to obtain better outgassing. Also, a IO-in. oil diffusion pump was used instead of the original 4-in. pump. This allowed the reaction cell to be operated at higher pressures than previously while maintaining a pressure of 5 x 10e6 torr or less in the vacuum chamber. I N Tang and A W Castleman, J Chem Phys, 60 (lo), 1974,3981-3986. 41 229. Large angle inelastic scattering of Na+ by D2. (USA) Results are reported for large angle scattering of Na+ by Dz, HD and H, in the initial relative energy range of 0.74-16.9 eV. It is concluded that perpendicular (C,,)ratherthan collinear conformations of the Na+-D2 system produce the most intense inelastic scattering. Results are given for exact classical trajectory calculations. The apparatus consisted of an ion source, a cell and a detection system. These were mounted on the lid of a IO-in. stainless vacuum can. The system was pumped by a 6-in. oil diffusion pump protected by a liquid nitrogen cooled baffle, and was baked at 125°C for 12 h prior to experiments. Operating pressures were less than lo-’ torr. W L Dimpfl and B H Mahan, J Chem Phys, 60 (8), 1974, 3238-3250. 41 230. Molecular beam study of the K-CF,I reaction: Detailed differential reaction cross section and energy disposal. (USA) The reaction of a velocity-selected K beam with a crossed beam of CFBI (from a thermal capillary-array source) was studied by the velocity-analysis technique. The KI product flux was transformed to yield the center-of-mass (cm) detailed differential reactions cross section. The cm cross section is “backward” peaked, but there is a substantial reactive contribution in the forward hemisphere as well. The average released into translational recoil of the products is only 8.5 kcal/mole, so that some 70% of the total available energy is partitioned into internal degrees of freedom of the products. The basic apparatus has been previously described and suitable references are given. AG A M Rulis et al, J Chem Phys, 60 (7), 1974, 2822-2827. 41 231. Theory of current characteristics of a thin dielectric film under slow electron impact. A relation between the current transmitted by a thin dielectric film as a function of incident electron energy and the electronic energy structure of the film is derived. These current characteristics have been measured by W H Hamill et al (References given). For low energies, l-4 eV, it is found that the current characteristics are insensitive to the detailed energy structure of the solid. In the moderately high energy range 4-10 eV, the transmitted current is more sensitive to the energy levels of the solid, but the relation is not straight-forward, involving a convolution of a joint density of states and a conduction band density of states. M E Harrigan, J Chem Phys, 60 (12), 1974, 49094919. 42. GLASS, CERAMICS AND REFRACTORY
OXIDES
42~23 232. Method of manuthcturing an insulator. (USSR) A vacuum-tight insulator based on vacuum-melted stainless steel is described. Art enamel of the following composition is deposited on the steel: SiO, 61.8-65.8. Al,O, 6.6-7.5. B20, 2.2-3.7. CaO 4.9-5.5. BaO 6.5-9.6; MnO 2.6-3.3, Na,O 317-4.5, K20 3.0-4.5, Li2d 0.5-1.0, MOO* 0.14.2 wt. %; this is then roasted at lOOO-1OlO’C. A slightly different enamel is then deposited: SiOl 58.7-61.4, A1,03 4.6-5.8, B203 0.9-2.4, CaO 3.8-4.8, NazO 17.5-18.4, K20 0.6-1.6, TiOl 7.1-8.2, Co203 0.8-1.3, Moo9 0.6-0.7; this is roasted at 84&85o”C. The enamels are prepared by wet-milling the components in a ball mill, diluted with distilled water to the desired viscosity, and left standing for 24 h. Before application the metal surface is sandblasted and degreased. After heat treatment the enamel is allowed to cool with the furnace; its total thickness is 500 pm. I P Chelpanov et al, Soviet Patent, class H 01 b, 17126, C 03 c, 7100, No. 375686, claimed 10th March 1970, publd 11th May 1973 (in Russian).