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155. CsF, Cs as a low work funstion layer on the GaAs photocathode
Classified
abstracts
145-155
wave moving in the direction of plasma drift in crossed electric and magnetic fields. Azimuthal modes with m= 1, 2, 3 are observed. The dependence of the critical magnetic field for the onset of oscillations on discharge parameters is measured. The regions of discharge parameters for the existence of different mode oscillations are determined. The data on behaviour of the frequency and amplitude of oscillations with changing discharge conditions and also the effect of the latter on plasma parameters are obtained. V G Naumovets et al, Ukruin Fiz Zh, 15 (3), 1970, 377-390 (in Ukrainian). 18 145. Investigation of optical inhomogeneities of the active substance in
a CF,I photodissociation laser. (USSR) Effects connected with photodissociation of CF,I in the pressure range from 15 to 120 torr are investigated. It is found that in CF,I contaminated with dissociation products, a shock wave appears due to evaporation of molecular iodine adsorbed on chamber walls on irradiation by a laser light. I M Belousova et al, Zh Eksper Tear Fiz, 58 (5), Mqv 1970, 1481-1486 (in Russian). 18
146. On the mechanism of formation of a hot electron component in the interaction between an electron beam and plasma. (USSR) Results of experimental investigation of oscillation spectra excited by an electron beam in a plasma under conditions, when a hot electron component appears, are presented. A mechanism of the hot electron component formation based on scattering of beam electrons by electrostatic oscillations, capture of part of electrons in negative traps and their subsequent heating during resonance interaction with waves, is given. A N Karkhov, Zh Eksper Tear Fiz, 59 (2), Aug 1970, 356-365 (in Russian). 18 147. Ionization collisions and charge exchange of Li+, Liz+ and Li3+ ions in gases (0.2-2 MeV). (USSR)
The effective cross sections for formation of slow positive ions and free electrons during ionization of Hz, N,, He, Ar and Kr gases by lithium ions with energy of 0.2 to 2 MeV are measured. The experimental apparatus for the study of collision phenomena is described. L I Pivovar et al, Zh Eksper Teor Fiz, 59 (7), June 1970, 19-28 (in Russian). 18 148. Formation of highly excited 30-180 keV helium atoms during
charge exchange and their ionization in a strong electric field. (USSR) Formation of highly excited helium atoms during charge exchange of 30 to 180 keV He+ ions on neon, sodium or magnesium atoms is investigated. Some features of highly excited helium atom ionization by a strong electric field are discussed. R N Ilin et al, Zh Eksper Teor Fiz, 59 (I), July 1970, 103-109 (in Russian). 18 149. On control of chemical reactions by resonance photo-action on
molecules. (USSR) The possibility of carrying out chemical reaction in rarefied gases by application of resonance infrared laser radiation is considered. The action of coherent radiation results in weakening of the chosen bond and a sharp increase in the reaction rate. N D Artamonova et al. Zh Ekmer Teor Fiz. 58 (6). June 1970. 21952201 (in Russian). 18 150. Excitation of Lee line during stripping of fast negative hydrogen
ions in inert gases. (USSR) Processes of fast negative ion stripping during their passage through the gas target at low pressure are investigated. The intensity of the Lyman a-line, emitted in collisions between fast hydrogen negative ions with energy of 5 to 40 keV and inert gases at pressure from I x 10m4 to 6 x lo-* torr, is measured. A L Orbeli et al, Zh Eksper Teor Fiz, 58 (6), June 1970, 1938-1942 (in Russian). 18
151. Method of infrared diagnostics of plasma and its application for investigation of ionization and recombination of xenon behind the front of shock wave. (USSR) A method for determination of electron temperature and concentration profiles behind the front of a shock wave is described. It is based 142
on simultaneous measurement of emission and absorption in the infrared region of the spectrum by the ionized gas. Results of experimental investigations of ionization and recombination processes in xenon at pressure of 3 torr and temperature of 8200 to 9200°K are given. N A Generalov et al, Zh Eksper Tear Fiz, 58 (6), June 1970, 1928-l 937 (in Russian). 18 152. Nature of ionization in a photoresonant caesium plasma.
(USSR) Nature of ionization in a photoresonant caesium plasma is studied in the pressure range of 10e2 to 10-l torr. Molecular and atomic caesium ions are detected in the plasma by the mass spectrometer technique. Properties of the plasma electron gas are determined. N D Morgulis and A M Przhonskiy, Zh Eksper Teor Fiz, 58 (6), June 1970, 1873-1878 (in Russian). I8 153. Polarization selectivity of external two-quantum photoeffect in
metals. (USSR) It is shown that polarization selectivity of the external two-quantum photoeffect from metallic surfaces is characterized by a pronounced optimum orientation of electric field intensity vector with a considerable increase of photocurrent. P P Barashev, Fiz Tverd Tela, 12 (7), Jury 1970, 1973-1976 (in Russian). 18 154. External photoeffect of LiF and MgFz films in the spectral region of 15 to 220 nm. (USSR)
Spectral distribution of the quantum yield from LiF and MgFz films was investigated in the broad spectral region of 15 to 220 nm. Samples were prepared by evaporation of dielectric films on metallic plates in vacuum at pressure of 1 x 10d5 torr. MgF, layers were prepared also by evaporation on heated substrates to 250-300°C. Measurements of quantum yield were carried out by monochromators. An open photoelectron multiplier and cathodoluminescence transducer were used as detectors. In the long wavelength region, where the layers are optically transparent, photoemission is determined by lattice defects in the layer originating from stoichiometric disturbances, incurred during the various technology operations, and substrate photoemission passing through the layers. In the region of absorption by the layers, where photon energy is greater than the forbidden energy band, a series of maxima is observed due to transitions from the valence and deep bands to the conduction band and electron plasma oscillation excitation. At photon energy greater than 35 eV, Auger electrons are observed. In this region of photon energy, electronelectron scattering is found to play a role in photoemission. It is concluded that decisions on the mechanism of photoemission at high photon energies can only be made after investigation of the energy histribution of photoelecirons. V A Blank and 0 M Sorokin, Fiz Tverd Tela, 12 (7), July 1970, 193 I 1936 (in Russian). I8 155. CsF, Cs as a low work function layer on the GaAs photocathode. (Germany) Adsorbed films of CsF covered with a monolayer of Cs on GaAs reduce the work function to a value of I eV. CsF layers were prepared by vacuum evaporation of CsF from a platinum or tantalum sleeve with holes. Cs was applied by means of a cesium chromate-silicon source or a Cs-AlzOs-Pt ion gun. The dependence of the quantum yield on photon energy shows that the threshold is at 1.0 eV with a break in the curve at 1.4 eV. The lower value is attributed to the threshold for emission from surface states, while the break point gives the onset of valence band photoemission. The Fermi level position is less than 0.4 eV above the valence band edge at the surface. For CsF, Cs on p-type GaAs the optimum electron escape probability is 0.5 for cleaved crystals in ultrahigh vacuum in the doping range between 1.3 x lo’* and 5.1 x lOlo cme3. For mixed crystals of Ga0.851n0.,PAs the threshold photoemission was reduced to 1.1 eV. High quantum efficiencies are obtained. The Ga,.&,.,,As vacuum cleaved crystal covered with CsF, Cs gave white light sensitivity of 443 ~~A/lrn with an escape probability of 0.435 and a diffusion length of I.1 x 10m5cm. Also GaAs epitaxial layers bombarded with argon ions, and heated, can be favourably activated by CsF, Cs layers. It is shown that a very thin CsF, Cs layer on GaAs is thermally stable and increases the potentialities of the GaAs photocathode. S Garbe, Phvs Stat Sol (a), 2 (3), July 1970,497-501.
abstracts
145-155
wave moving in the direction of plasma drift in crossed electric and magnetic fields. Azimuthal modes with m= 1, 2, 3 are observed. The dependence of the critical magnetic field for the onset of oscillations on discharge parameters is measured. The regions of discharge parameters for the existence of different mode oscillations are determined. The data on behaviour of the frequency and amplitude of oscillations with changing discharge conditions and also the effect of the latter on plasma parameters are obtained. V G Naumovets et al, Ukruin Fiz Zh, 15 (3), 1970, 377-390 (in Ukrainian). 18 145. Investigation of optical inhomogeneities of the active substance in
a CF,I photodissociation laser. (USSR) Effects connected with photodissociation of CF,I in the pressure range from 15 to 120 torr are investigated. It is found that in CF,I contaminated with dissociation products, a shock wave appears due to evaporation of molecular iodine adsorbed on chamber walls on irradiation by a laser light. I M Belousova et al, Zh Eksper Tear Fiz, 58 (5), Mqv 1970, 1481-1486 (in Russian). 18
146. On the mechanism of formation of a hot electron component in the interaction between an electron beam and plasma. (USSR) Results of experimental investigation of oscillation spectra excited by an electron beam in a plasma under conditions, when a hot electron component appears, are presented. A mechanism of the hot electron component formation based on scattering of beam electrons by electrostatic oscillations, capture of part of electrons in negative traps and their subsequent heating during resonance interaction with waves, is given. A N Karkhov, Zh Eksper Tear Fiz, 59 (2), Aug 1970, 356-365 (in Russian). 18 147. Ionization collisions and charge exchange of Li+, Liz+ and Li3+ ions in gases (0.2-2 MeV). (USSR)
The effective cross sections for formation of slow positive ions and free electrons during ionization of Hz, N,, He, Ar and Kr gases by lithium ions with energy of 0.2 to 2 MeV are measured. The experimental apparatus for the study of collision phenomena is described. L I Pivovar et al, Zh Eksper Teor Fiz, 59 (7), June 1970, 19-28 (in Russian). 18 148. Formation of highly excited 30-180 keV helium atoms during
charge exchange and their ionization in a strong electric field. (USSR) Formation of highly excited helium atoms during charge exchange of 30 to 180 keV He+ ions on neon, sodium or magnesium atoms is investigated. Some features of highly excited helium atom ionization by a strong electric field are discussed. R N Ilin et al, Zh Eksper Teor Fiz, 59 (I), July 1970, 103-109 (in Russian). 18 149. On control of chemical reactions by resonance photo-action on
molecules. (USSR) The possibility of carrying out chemical reaction in rarefied gases by application of resonance infrared laser radiation is considered. The action of coherent radiation results in weakening of the chosen bond and a sharp increase in the reaction rate. N D Artamonova et al. Zh Ekmer Teor Fiz. 58 (6). June 1970. 21952201 (in Russian). 18 150. Excitation of Lee line during stripping of fast negative hydrogen
ions in inert gases. (USSR) Processes of fast negative ion stripping during their passage through the gas target at low pressure are investigated. The intensity of the Lyman a-line, emitted in collisions between fast hydrogen negative ions with energy of 5 to 40 keV and inert gases at pressure from I x 10m4 to 6 x lo-* torr, is measured. A L Orbeli et al, Zh Eksper Teor Fiz, 58 (6), June 1970, 1938-1942 (in Russian). 18
151. Method of infrared diagnostics of plasma and its application for investigation of ionization and recombination of xenon behind the front of shock wave. (USSR) A method for determination of electron temperature and concentration profiles behind the front of a shock wave is described. It is based 142
on simultaneous measurement of emission and absorption in the infrared region of the spectrum by the ionized gas. Results of experimental investigations of ionization and recombination processes in xenon at pressure of 3 torr and temperature of 8200 to 9200°K are given. N A Generalov et al, Zh Eksper Tear Fiz, 58 (6), June 1970, 1928-l 937 (in Russian). 18 152. Nature of ionization in a photoresonant caesium plasma.
(USSR) Nature of ionization in a photoresonant caesium plasma is studied in the pressure range of 10e2 to 10-l torr. Molecular and atomic caesium ions are detected in the plasma by the mass spectrometer technique. Properties of the plasma electron gas are determined. N D Morgulis and A M Przhonskiy, Zh Eksper Teor Fiz, 58 (6), June 1970, 1873-1878 (in Russian). I8 153. Polarization selectivity of external two-quantum photoeffect in
metals. (USSR) It is shown that polarization selectivity of the external two-quantum photoeffect from metallic surfaces is characterized by a pronounced optimum orientation of electric field intensity vector with a considerable increase of photocurrent. P P Barashev, Fiz Tverd Tela, 12 (7), Jury 1970, 1973-1976 (in Russian). 18 154. External photoeffect of LiF and MgFz films in the spectral region of 15 to 220 nm. (USSR)
Spectral distribution of the quantum yield from LiF and MgFz films was investigated in the broad spectral region of 15 to 220 nm. Samples were prepared by evaporation of dielectric films on metallic plates in vacuum at pressure of 1 x 10d5 torr. MgF, layers were prepared also by evaporation on heated substrates to 250-300°C. Measurements of quantum yield were carried out by monochromators. An open photoelectron multiplier and cathodoluminescence transducer were used as detectors. In the long wavelength region, where the layers are optically transparent, photoemission is determined by lattice defects in the layer originating from stoichiometric disturbances, incurred during the various technology operations, and substrate photoemission passing through the layers. In the region of absorption by the layers, where photon energy is greater than the forbidden energy band, a series of maxima is observed due to transitions from the valence and deep bands to the conduction band and electron plasma oscillation excitation. At photon energy greater than 35 eV, Auger electrons are observed. In this region of photon energy, electronelectron scattering is found to play a role in photoemission. It is concluded that decisions on the mechanism of photoemission at high photon energies can only be made after investigation of the energy histribution of photoelecirons. V A Blank and 0 M Sorokin, Fiz Tverd Tela, 12 (7), July 1970, 193 I 1936 (in Russian). I8 155. CsF, Cs as a low work function layer on the GaAs photocathode. (Germany) Adsorbed films of CsF covered with a monolayer of Cs on GaAs reduce the work function to a value of I eV. CsF layers were prepared by vacuum evaporation of CsF from a platinum or tantalum sleeve with holes. Cs was applied by means of a cesium chromate-silicon source or a Cs-AlzOs-Pt ion gun. The dependence of the quantum yield on photon energy shows that the threshold is at 1.0 eV with a break in the curve at 1.4 eV. The lower value is attributed to the threshold for emission from surface states, while the break point gives the onset of valence band photoemission. The Fermi level position is less than 0.4 eV above the valence band edge at the surface. For CsF, Cs on p-type GaAs the optimum electron escape probability is 0.5 for cleaved crystals in ultrahigh vacuum in the doping range between 1.3 x lo’* and 5.1 x lOlo cme3. For mixed crystals of Ga0.851n0.,PAs the threshold photoemission was reduced to 1.1 eV. High quantum efficiencies are obtained. The Ga,.&,.,,As vacuum cleaved crystal covered with CsF, Cs gave white light sensitivity of 443 ~~A/lrn with an escape probability of 0.435 and a diffusion length of I.1 x 10m5cm. Also GaAs epitaxial layers bombarded with argon ions, and heated, can be favourably activated by CsF, Cs layers. It is shown that a very thin CsF, Cs layer on GaAs is thermally stable and increases the potentialities of the GaAs photocathode. S Garbe, Phvs Stat Sol (a), 2 (3), July 1970,497-501.