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Molecule-atom total scattering cross sections: LiF on Ar, Kr and N2
Classified abstracts 94-107 33
94. Electric deflection of binary hexafluorides Two different apparatuses were used to study the behavlour of molecular beams m m h o m o g e n e o u s electric fields. In both cases, mass analysis was used. The binary hexafluorides of SF6, SeF6, TeFs, MoF6, WF6, UF6, RuFf, RhF6, ReF6, OsF6, lrF6 and PtF6 were studied In no case was refocusing of the molecular beam observed when an electric field was applied. E W Kaiser et al, J Chem Phys, 53 (4), 15 Aug 1970, 1411-1412 33 95. The influence of interaction between molecules (atoms) on the effieiene) of quantum beam generator operation. (USSR) The influence of interaction between molecules or atoms on the efficiency of the sorting system in a molecular or atom q u a n t u m beam generator is investigated. A m m o n i a molecule beam dependence on the beam current from the source to the sorting systcm, and on the p u m p i n g speed of the vacuum system, are measured. B 1 Semenov, Zh tekh Ftz, 40 (7), July 1970, 1396-1401 (tit Russian). 33 96. X-Ray photoelectron spectroscopy of carbon monoxide The ionization potentials for all of the electrons of carbon monoxide have been measured by X-ray photoelectron spectroscopy Measurements are reported, m electron volts, for oxygen ls and carbon Is. The binding energies were determined by lrradmtlon of a gaseous sample with magnesium Ka X-rays and by measuring the kinetic energies of the photoelectrons with an iron-free double-focusing spectrometer of 50-cm radius. T D Thomas, J Chem Phys', 53 (5), 1 Sept 1970, 1744-1749 33
97. Low-energy electron-reflection spectrometry for thin films of aromatic and aliphatic molecules at 77°K Low-energy electron reflechon (LEER) spectra were measured for thin films of pyrtdine, mesyttylene, toluene, aniline, I-hexane, cyclohexane, 2-methylpentane and cyclohexane at 7 T K Dlfferentml plots show clearly defined peaks which appear to correspond to nearresonant energy losses These results are discussed at some length and energy values are given The apparatus and techniques used have been described previously. The pressure in the spectrometer was less than 10 " t o r r prior to and during all measurements D Lewis et al, J Chem Phys, 53 (7), 1 Oct 1970, 275~2756. 33 98. Improvements in an electron microscope for clean, quiet, vibrationless operation. (USA) A new vacuum system has been designed and constructed for a Siemens Elmtskop I electron microscope in order to provide a cleaner environment about the specimen during normal use of the instrument, and to prepare the instrument for the addition of an ultrahigh vacuum specimen chamber for in situ film growth studies. Liquid nitrogen sorptton p u m p s are used on the upper and lower parts of the microscope column, and an O r b - I o n p u m p Is used to p u m p differentially on the large specimen chamber. An impedance tube at the top and another at the b o t t o m of the chamber restrict the gas flow rate to 7 10 ~ htre/sec. Under operating conditions the pressure m the upper and lower parts of the microscope is less than2 10 ~ torr, m the specimen chamber Is less than 2 10 ~ torr, the hydrocarbon contamination rate is about 0.7 A,/mm, the specimen changing time is 2 ram, and the plate changing time ~s 4 ram. R B Marcus et al, Rev ~ tent lnstrum, 41 (9), 1970, 1319-1323 33 99. Low-energy electron diffraction study of tungsten (1003 surface. The sample surface was cleaned by repeatedly heating to 2300~K in high vacuum. Instrumental factors and the effect of ambient gases on intensmes were checked. The (100) beam intensity profile was measured in the energy range 100-300 eV for sequences of primary-beam orientation Special effects associated with the simultaneous occurrence of different Bragg conditions were found P S P Wei, J Chem Phys, 53 (7), 1 Oct 1970, 2939-2945. 33 100. Photofragment spectrometer. (USA) An apparatus for photofragment spectroscopy, a new type of molecular spectroscopy for dissociative electronic states, is described. Inside an ultrahigh vacuum system, a molecular beam is crossed by pulses of polarized hght and the recodmg photodlssociahon fragments are detected by a quadrupole mass spectrometer a few centmaetres away. Colhstonless recoil Js ensured in the interaction chamber m which the 68
molecular and light beams cross, by maintaining pressures of 10 8 10 -6 torr with the molecular beam on To mlmmlze noise the detector chamber containing the mass spectrometer is p u m p e d separately, maintaining a total pressure of 10-H-10 8 torr and a partial pressure of the mass of interest of 10-~°-10 " torr These detector pressures are maintained by high speed differential p u m p i n g even though the molecular beam with an equivalent pressure of a b o u t 2 10 ' torr is but a few cent~metres away. G E Busch et al, Rev sctent Instrum, 41 (7), 1970, 1066-1073. 33
101. Convolution analysis of electron experiments This is a theoretical paper concerned with the analysis of electron Impact experiments from the wewpolnt of the influence of the electron beam energy dlstrlbuuon. A generalized electron energy distribution function ~s formulated. Special cases of this distribution function yield analytical representations of operational electron guns. The energy d~strtbutton of the gun is found to strongly affect the sahent features of the cross section. R L Cowperthwaite and H Myers, J Chem Phys, 53 (3), I 4u~,, 1970,
1077-1082. 33 102. The hollow thermionic cathode system used in thyratrons. (Great Britain) A simple explanation for the high currents obtained from hydrogen thyratron cathodes is put forward, it is suggested that the "'hollowness" of the cathode structure and the high secondary emission coefficient for low energy hydrogen ions incident on barium covered surfaces leads to a self-maintained discharge with modest running voltage. J Gowar, J Plow D, Appl Phvs, 3 (9), 1970, L37-39. 33 103. Neutral particle density modulation in the positive column of a low-pressure mercury discharge modulated at low frequencies. (Great Brltam) Pyrex discharge tubes fitted with nickel anodes were used. The tubes were well cleaned and evacuated to a residual gas pressure of less than 10 6 torr. The experiments show a clockwise hysteresis between electron n u m b e r density and discharge current in the positive column of the mercury discharge modulated at low frequencies J R Riley, J Phl's D, Appl Phy~, 3 (8), 1970, 1226-1239. 33 104. Generating cold gas for photomultiplier cooling. (USA) The somewhat unused techmque for generating cold gas by bubbling room temperature N2 directly Into liquid nitrogen, offers twice the cooling time of the conventional immersed heater or continuous gas flow t h r o u g h systems. J Gerber, Rev sctent htstrum, 41 (7), 1970, 916 33 105. Molecule-atom total scattering cross sections: LiF on Ar, Kr and N2 Total quantum-mechamcal scattering cross sections of LIF on At, Kr and N2 were measured as a function of colhslonal velocity m the thermal energy range, to about 1 2 per cent accuracy, through the use of circular bearn geometry and a McLeod gauge to measure target ga ~, density. G o o d agreement was obtained at only the lowest experimental velocity At higher velocihes the cross section is larger than predicted. E Riehman and L Wharton, J Chem Phys, 53 (3), I Aug 1970, 945-956
34. H I G H A L T I T U D E AND S P A C E T E C H N O L O G Y 34
106. Research on hollow cathodes in mercury ion thrusters.
(USA)
In an effort to improve thruster performance by the redtlctlon of discharge and impingement losses, the effects of grid spacing, accelerator potential, cathode flow rate, and main magnetic field intensity were considered T h r o u g h an investigation of these parameters, a base operating condition has been established. W R Mickelsen and G Palumbo, Rep NASA-CR-I09627, Mat 1970, 69 ages (Scl Tech Aero.space Rep~, 8 (12), 2286, N70-25703) 34
107. A plasma-beam system for simulating the interaction of a spacecraft with the ionosphere. (Netherlands) An argon-~on beam, extracted from an electron-bombaldment ion bource, was neutrahzed by electrons to form a colhs~onless plasma stream characterized by a well-ordered Ion motion The neutrahzmg
94. Electric deflection of binary hexafluorides Two different apparatuses were used to study the behavlour of molecular beams m m h o m o g e n e o u s electric fields. In both cases, mass analysis was used. The binary hexafluorides of SF6, SeF6, TeFs, MoF6, WF6, UF6, RuFf, RhF6, ReF6, OsF6, lrF6 and PtF6 were studied In no case was refocusing of the molecular beam observed when an electric field was applied. E W Kaiser et al, J Chem Phys, 53 (4), 15 Aug 1970, 1411-1412 33 95. The influence of interaction between molecules (atoms) on the effieiene) of quantum beam generator operation. (USSR) The influence of interaction between molecules or atoms on the efficiency of the sorting system in a molecular or atom q u a n t u m beam generator is investigated. A m m o n i a molecule beam dependence on the beam current from the source to the sorting systcm, and on the p u m p i n g speed of the vacuum system, are measured. B 1 Semenov, Zh tekh Ftz, 40 (7), July 1970, 1396-1401 (tit Russian). 33 96. X-Ray photoelectron spectroscopy of carbon monoxide The ionization potentials for all of the electrons of carbon monoxide have been measured by X-ray photoelectron spectroscopy Measurements are reported, m electron volts, for oxygen ls and carbon Is. The binding energies were determined by lrradmtlon of a gaseous sample with magnesium Ka X-rays and by measuring the kinetic energies of the photoelectrons with an iron-free double-focusing spectrometer of 50-cm radius. T D Thomas, J Chem Phys', 53 (5), 1 Sept 1970, 1744-1749 33
97. Low-energy electron-reflection spectrometry for thin films of aromatic and aliphatic molecules at 77°K Low-energy electron reflechon (LEER) spectra were measured for thin films of pyrtdine, mesyttylene, toluene, aniline, I-hexane, cyclohexane, 2-methylpentane and cyclohexane at 7 T K Dlfferentml plots show clearly defined peaks which appear to correspond to nearresonant energy losses These results are discussed at some length and energy values are given The apparatus and techniques used have been described previously. The pressure in the spectrometer was less than 10 " t o r r prior to and during all measurements D Lewis et al, J Chem Phys, 53 (7), 1 Oct 1970, 275~2756. 33 98. Improvements in an electron microscope for clean, quiet, vibrationless operation. (USA) A new vacuum system has been designed and constructed for a Siemens Elmtskop I electron microscope in order to provide a cleaner environment about the specimen during normal use of the instrument, and to prepare the instrument for the addition of an ultrahigh vacuum specimen chamber for in situ film growth studies. Liquid nitrogen sorptton p u m p s are used on the upper and lower parts of the microscope column, and an O r b - I o n p u m p Is used to p u m p differentially on the large specimen chamber. An impedance tube at the top and another at the b o t t o m of the chamber restrict the gas flow rate to 7 10 ~ htre/sec. Under operating conditions the pressure m the upper and lower parts of the microscope is less than2 10 ~ torr, m the specimen chamber Is less than 2 10 ~ torr, the hydrocarbon contamination rate is about 0.7 A,/mm, the specimen changing time is 2 ram, and the plate changing time ~s 4 ram. R B Marcus et al, Rev ~ tent lnstrum, 41 (9), 1970, 1319-1323 33 99. Low-energy electron diffraction study of tungsten (1003 surface. The sample surface was cleaned by repeatedly heating to 2300~K in high vacuum. Instrumental factors and the effect of ambient gases on intensmes were checked. The (100) beam intensity profile was measured in the energy range 100-300 eV for sequences of primary-beam orientation Special effects associated with the simultaneous occurrence of different Bragg conditions were found P S P Wei, J Chem Phys, 53 (7), 1 Oct 1970, 2939-2945. 33 100. Photofragment spectrometer. (USA) An apparatus for photofragment spectroscopy, a new type of molecular spectroscopy for dissociative electronic states, is described. Inside an ultrahigh vacuum system, a molecular beam is crossed by pulses of polarized hght and the recodmg photodlssociahon fragments are detected by a quadrupole mass spectrometer a few centmaetres away. Colhstonless recoil Js ensured in the interaction chamber m which the 68
molecular and light beams cross, by maintaining pressures of 10 8 10 -6 torr with the molecular beam on To mlmmlze noise the detector chamber containing the mass spectrometer is p u m p e d separately, maintaining a total pressure of 10-H-10 8 torr and a partial pressure of the mass of interest of 10-~°-10 " torr These detector pressures are maintained by high speed differential p u m p i n g even though the molecular beam with an equivalent pressure of a b o u t 2 10 ' torr is but a few cent~metres away. G E Busch et al, Rev sctent Instrum, 41 (7), 1970, 1066-1073. 33
101. Convolution analysis of electron experiments This is a theoretical paper concerned with the analysis of electron Impact experiments from the wewpolnt of the influence of the electron beam energy dlstrlbuuon. A generalized electron energy distribution function ~s formulated. Special cases of this distribution function yield analytical representations of operational electron guns. The energy d~strtbutton of the gun is found to strongly affect the sahent features of the cross section. R L Cowperthwaite and H Myers, J Chem Phys, 53 (3), I 4u~,, 1970,
1077-1082. 33 102. The hollow thermionic cathode system used in thyratrons. (Great Britain) A simple explanation for the high currents obtained from hydrogen thyratron cathodes is put forward, it is suggested that the "'hollowness" of the cathode structure and the high secondary emission coefficient for low energy hydrogen ions incident on barium covered surfaces leads to a self-maintained discharge with modest running voltage. J Gowar, J Plow D, Appl Phvs, 3 (9), 1970, L37-39. 33 103. Neutral particle density modulation in the positive column of a low-pressure mercury discharge modulated at low frequencies. (Great Brltam) Pyrex discharge tubes fitted with nickel anodes were used. The tubes were well cleaned and evacuated to a residual gas pressure of less than 10 6 torr. The experiments show a clockwise hysteresis between electron n u m b e r density and discharge current in the positive column of the mercury discharge modulated at low frequencies J R Riley, J Phl's D, Appl Phy~, 3 (8), 1970, 1226-1239. 33 104. Generating cold gas for photomultiplier cooling. (USA) The somewhat unused techmque for generating cold gas by bubbling room temperature N2 directly Into liquid nitrogen, offers twice the cooling time of the conventional immersed heater or continuous gas flow t h r o u g h systems. J Gerber, Rev sctent htstrum, 41 (7), 1970, 916 33 105. Molecule-atom total scattering cross sections: LiF on Ar, Kr and N2 Total quantum-mechamcal scattering cross sections of LIF on At, Kr and N2 were measured as a function of colhslonal velocity m the thermal energy range, to about 1 2 per cent accuracy, through the use of circular bearn geometry and a McLeod gauge to measure target ga ~, density. G o o d agreement was obtained at only the lowest experimental velocity At higher velocihes the cross section is larger than predicted. E Riehman and L Wharton, J Chem Phys, 53 (3), I Aug 1970, 945-956
34. H I G H A L T I T U D E AND S P A C E T E C H N O L O G Y 34
106. Research on hollow cathodes in mercury ion thrusters.
(USA)
In an effort to improve thruster performance by the redtlctlon of discharge and impingement losses, the effects of grid spacing, accelerator potential, cathode flow rate, and main magnetic field intensity were considered T h r o u g h an investigation of these parameters, a base operating condition has been established. W R Mickelsen and G Palumbo, Rep NASA-CR-I09627, Mat 1970, 69 ages (Scl Tech Aero.space Rep~, 8 (12), 2286, N70-25703) 34
107. A plasma-beam system for simulating the interaction of a spacecraft with the ionosphere. (Netherlands) An argon-~on beam, extracted from an electron-bombaldment ion bource, was neutrahzed by electrons to form a colhs~onless plasma stream characterized by a well-ordered Ion motion The neutrahzmg