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Absolute measurements of total cross section for electron scattering by Na2 and K2 (0.5–50 eV)
Classified abstracts 138-l
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nitrogen. The variation of the temperature is less than 52°C in the whole temperature range. To ensure good heat insulation, the loading rod is divided by a system of steel rings interspaced with glass balls. First results with an aluminium alloy are presented. (Germany) V Bachmann et al, Rev Sci Instrum, 45 (5), 1974,702-704.
IV. Materials and techniques vacuum technology
used in
40. GASES AND VAPOURS 40 __^ 1% Uynamics of the 0’ - I-I2 reaction. II. Reactive and nonreactive scattering of 0+(4S3,2> at relative energies above 13 eV. (USA) Velocity vector distributions for the reactive and nonreactive scattering of O+ by Hz, D2 and HD in the relative energy range 13-50 eV are reported. Essentially no very small angle reactive scattering is observed for any of these systems. In the lower and intermediate parts of the energy range, the product of the O+(DZ, D) OD+ reaction reaches a maximum intensity near SO”, and decreases somewhat at larger angles. The shape is maintained but with decreasing intensity from 15-30 eV relative energy. At higher energies, the distribution moves to larger angles and the intensity continues to drop. The results are presented principally in the form of contour maps of the specific intensity I@, u), the intensity of ions per unit velocity space volume normalized to unit beam strength, scattering gas intensity and collision volume. The experiments were performed by allowing a collimated, energy selected beam of O+ ions to impinge on a target gas in a scattering ceii. J Chem Phys, 59 (12), 1973, 6380-6396. 40 139. Ion-molecule reactions in perdeuteriomethane. (USA) Ion cyclotron resonance techniques were used to measure absolute rate constants for the reactions-(l) CD.,+ + CD4 -+ CD,+ + CDS and (2) CD1+ + CD q-+ C?Dq+ + D,. Rate coefficients deduced from.the appearance if product ions aid disappearance of reactant ions were identical within experimental error, confirming the assumption that these are the only significant reactions of thermal energy CD4 and CDB, respectively. The magnitudes of the rate constants, kI = 1.1 x 10ep cm3 mol-’ set-’ and kZ = 1.2 x 10mp cm3 mol-’ set-’ are consistent with the simple polarization theory of ion-molecule reactions (and with previous measurements). J H Futrell, J Chem Phys, 59 (8), 1973,4061+063. 40 140. Molecular electron affinities from collisiona! ionization of ce&uu, I. NO, NO,, and NzO*. (USA) The relative cross sections for the production of parent negative ions and O- fragment ions resulting from collisions of fast cesium atoms with Maxwellian target gases of NO, NOz and N20 were studied as a function of the incident cesium beam energy from 0 to -40 eV. A charge exchange source was used to produce the atomiccesium beam, and the energy distribution of the cesium beam was determined by a time-of-flight analysis. A time-of-flight mass spectrometer using ion counting methods was used to identify the masses of the ions. Lower limits for the electron affinities of NO, NO* and NzO were found to be 0.1 f 0.1, 215.0.1 and -0.15 f 0.1 eV, respectively. The affect of Doppler motion of the target gas is discussed. S J Nalley et al, J Chem Phys, 59 (8), 1973,41254139. 40 141. Absolute measurements of total cross section for electron rratt~rino hv Nn _ nnrl K_ ffi c61-I ocr\ lT TCA> I-.‘---..~ “_, ‘.“L U.” s-1 \“..z “V .,.I. \“Y”, The measurements noted were made in the electron energy range 0.5-50 eV at temperatures of 405 and 335°C respectively, using the molecular beam recoil technique. It was found that the molecular cross sections were about 60% and 33 ‘A above the respective sodium and potassium atomic cross sections above 2 eV. The molecular cross sections for sodium and potassium ranged from 305 to 430 A’, respectively, at 0.5 eV and 85 and 97 A2, respectively, at 50 eV. The overall uncertainties in the dimer results are, at most, for sodium 16 % and for potassium 20 %. T M Millar and A Kasdan, J Chem Phys, 59 (8), 1973, 3913-3919. 46
40 142. Ionic collision processes in mixtures of hydrogen and rare gases. WA) Bimolecular reactions which occur in weakly ionized mixtures of (HZ + He), (He + Ne) (Hz + Ar) and (H, + Kr) were studied while the ions were contained in the space charge trap generated by the passage of a low energy electron beam through the ion source of a mass spectrometer. The results for (H, + He) and (Hz + Ne) agree with the reports from earlier studies. In (H, + Ar) and (HZ + Kr) mixtures the Hz ions were found to react with rate coefficients which are in good agreement with the polarization theory. Details of the apparatus used are given which was basically a research mass spectrometer. K R Ryan and I G Graham, J Chem Phys? 59 (81, 1973,426@4271. 40 143. Thermal energy positive ion reactions in a wet atmosphere containing ammonia. (USA) Rate constants for reactions of H+(HZO). with NH3, for n - 1 - 4, were measured at 296°K. Rate constants for NH4+(HzO)1,2 with NH, and the rate constant for NOz+(H20) + NH3 --f NH4+ + HNOB were also measured. A number of equilibrium constants were measured at 296°K. All of the measurements were carried out in a flowing afterglow system. The apparatus used has been described previously (Adv. At. Mol. Phys. 5, 1, 1969). Either O2 or CO, was used as the buffer gas, which was ionized by an electron gun. F C Fehsenfeld and E E Ferguson, J Chem Phys, 59 (12), 1973, 62726276. 40 144. Study of hydrogen diffusion in tantalum hydrides by inelastic neutron scattering. (USA) Neutron inelastic scattering was measured as a function of temperature and scattering angle for c( - TaH0.15 and for Ta,H in its Q and fl phases. The widths of the quasielastic peaks vs momentum transfer (Q) were derived and compared with several models for hydrogen diffusion. The results suggest the dominance of tetrahedral j;mps in the diffusion urocess. Residence times between 1.6 (340°C) and 4.0 (148°C) p&c for TaHo.ls and between 2.4 (300°C) and 7 (153°C) psec for TazH were derived from the fit of the observed widths to the tetrahedral model. These results indicate a significant concentration dependence of the diffusion rates in cc-TaH,. The neutron measurements were made with a hybrid time-of-flight spectrometer at the National Bureau of Standards nuclear reactor. J J Rush et al, J Chem Phys, 59 (12), 1973, 6570-6576. 40 145. Flow-drift technique for ion mobility and ion-molecule reaction rate constant measurements. I. Apparatus and mobility measurements. II. Positive ion reactions of N+, O+, and N,+ with O2 and O+ with N, from thermal to N 2 eV. III. Negative ion reactions of O- with CO, NO, H, and Dz. (USA) This is a series of three articles by the authors. The first describes the apparatus and techniques used. A flow-drift tube was used with a buffer gas (usually helium) maintained through the tube by means of a Roots-type blower backed by a mechanical pump. Tube pressures were in the range 0.19-1.25 torr. The drift-reaction section was terminated by an ion detection system capable of mass analysis. The positive ion-molecule reactions N* + 0, -+ NO* + 0 or 02*+N, N,*+O,+O,*+N,, O*+O,-+O,*+O and 0* + Nz + NO* + N were measured with the above apparatus. The first four reactions were measured from thermal energy to about 2 eV ion kinetic energy in the centre of mass. The last reaction was measured from 0.3-3 eV ion kinetic energy. The data agrees well with previous results. The third paper describes a combined flowing afterglow-drift tube experimental apparatus which was used to measure the reaction rate constants as a function of ion kinetic energy for the reactions of O- with CO, NO, Hz and DZ. The reaction rates are discussed in some detail. M McFarland et al, J Chem Phys, 59 (12), 1973,661&6635. 40 146. Bethe surface, elastic and inelastic differential cross sections, Compton profile and binding effects for HZ obtained by electron scattering with 25 keV incident electrons. (USA) Electron impact spectra for Hz were obtained at scattering angles of l”, l.S”, 2”, 3”, 4”, So, 7” and 100” using 25 keV incident electrons.
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nitrogen. The variation of the temperature is less than 52°C in the whole temperature range. To ensure good heat insulation, the loading rod is divided by a system of steel rings interspaced with glass balls. First results with an aluminium alloy are presented. (Germany) V Bachmann et al, Rev Sci Instrum, 45 (5), 1974,702-704.
IV. Materials and techniques vacuum technology
used in
40. GASES AND VAPOURS 40 __^ 1% Uynamics of the 0’ - I-I2 reaction. II. Reactive and nonreactive scattering of 0+(4S3,2> at relative energies above 13 eV. (USA) Velocity vector distributions for the reactive and nonreactive scattering of O+ by Hz, D2 and HD in the relative energy range 13-50 eV are reported. Essentially no very small angle reactive scattering is observed for any of these systems. In the lower and intermediate parts of the energy range, the product of the O+(DZ, D) OD+ reaction reaches a maximum intensity near SO”, and decreases somewhat at larger angles. The shape is maintained but with decreasing intensity from 15-30 eV relative energy. At higher energies, the distribution moves to larger angles and the intensity continues to drop. The results are presented principally in the form of contour maps of the specific intensity I@, u), the intensity of ions per unit velocity space volume normalized to unit beam strength, scattering gas intensity and collision volume. The experiments were performed by allowing a collimated, energy selected beam of O+ ions to impinge on a target gas in a scattering ceii. J Chem Phys, 59 (12), 1973, 6380-6396. 40 139. Ion-molecule reactions in perdeuteriomethane. (USA) Ion cyclotron resonance techniques were used to measure absolute rate constants for the reactions-(l) CD.,+ + CD4 -+ CD,+ + CDS and (2) CD1+ + CD q-+ C?Dq+ + D,. Rate coefficients deduced from.the appearance if product ions aid disappearance of reactant ions were identical within experimental error, confirming the assumption that these are the only significant reactions of thermal energy CD4 and CDB, respectively. The magnitudes of the rate constants, kI = 1.1 x 10ep cm3 mol-’ set-’ and kZ = 1.2 x 10mp cm3 mol-’ set-’ are consistent with the simple polarization theory of ion-molecule reactions (and with previous measurements). J H Futrell, J Chem Phys, 59 (8), 1973,4061+063. 40 140. Molecular electron affinities from collisiona! ionization of ce&uu, I. NO, NO,, and NzO*. (USA) The relative cross sections for the production of parent negative ions and O- fragment ions resulting from collisions of fast cesium atoms with Maxwellian target gases of NO, NOz and N20 were studied as a function of the incident cesium beam energy from 0 to -40 eV. A charge exchange source was used to produce the atomiccesium beam, and the energy distribution of the cesium beam was determined by a time-of-flight analysis. A time-of-flight mass spectrometer using ion counting methods was used to identify the masses of the ions. Lower limits for the electron affinities of NO, NO* and NzO were found to be 0.1 f 0.1, 215.0.1 and -0.15 f 0.1 eV, respectively. The affect of Doppler motion of the target gas is discussed. S J Nalley et al, J Chem Phys, 59 (8), 1973,41254139. 40 141. Absolute measurements of total cross section for electron rratt~rino hv Nn _ nnrl K_ ffi c61-I ocr\ lT TCA> I-.‘---..~ “_, ‘.“L U.” s-1 \“..z “V .,.I. \“Y”, The measurements noted were made in the electron energy range 0.5-50 eV at temperatures of 405 and 335°C respectively, using the molecular beam recoil technique. It was found that the molecular cross sections were about 60% and 33 ‘A above the respective sodium and potassium atomic cross sections above 2 eV. The molecular cross sections for sodium and potassium ranged from 305 to 430 A’, respectively, at 0.5 eV and 85 and 97 A2, respectively, at 50 eV. The overall uncertainties in the dimer results are, at most, for sodium 16 % and for potassium 20 %. T M Millar and A Kasdan, J Chem Phys, 59 (8), 1973, 3913-3919. 46
40 142. Ionic collision processes in mixtures of hydrogen and rare gases. WA) Bimolecular reactions which occur in weakly ionized mixtures of (HZ + He), (He + Ne) (Hz + Ar) and (H, + Kr) were studied while the ions were contained in the space charge trap generated by the passage of a low energy electron beam through the ion source of a mass spectrometer. The results for (H, + He) and (Hz + Ne) agree with the reports from earlier studies. In (H, + Ar) and (HZ + Kr) mixtures the Hz ions were found to react with rate coefficients which are in good agreement with the polarization theory. Details of the apparatus used are given which was basically a research mass spectrometer. K R Ryan and I G Graham, J Chem Phys? 59 (81, 1973,426@4271. 40 143. Thermal energy positive ion reactions in a wet atmosphere containing ammonia. (USA) Rate constants for reactions of H+(HZO). with NH3, for n - 1 - 4, were measured at 296°K. Rate constants for NH4+(HzO)1,2 with NH, and the rate constant for NOz+(H20) + NH3 --f NH4+ + HNOB were also measured. A number of equilibrium constants were measured at 296°K. All of the measurements were carried out in a flowing afterglow system. The apparatus used has been described previously (Adv. At. Mol. Phys. 5, 1, 1969). Either O2 or CO, was used as the buffer gas, which was ionized by an electron gun. F C Fehsenfeld and E E Ferguson, J Chem Phys, 59 (12), 1973, 62726276. 40 144. Study of hydrogen diffusion in tantalum hydrides by inelastic neutron scattering. (USA) Neutron inelastic scattering was measured as a function of temperature and scattering angle for c( - TaH0.15 and for Ta,H in its Q and fl phases. The widths of the quasielastic peaks vs momentum transfer (Q) were derived and compared with several models for hydrogen diffusion. The results suggest the dominance of tetrahedral j;mps in the diffusion urocess. Residence times between 1.6 (340°C) and 4.0 (148°C) p&c for TaHo.ls and between 2.4 (300°C) and 7 (153°C) psec for TazH were derived from the fit of the observed widths to the tetrahedral model. These results indicate a significant concentration dependence of the diffusion rates in cc-TaH,. The neutron measurements were made with a hybrid time-of-flight spectrometer at the National Bureau of Standards nuclear reactor. J J Rush et al, J Chem Phys, 59 (12), 1973, 6570-6576. 40 145. Flow-drift technique for ion mobility and ion-molecule reaction rate constant measurements. I. Apparatus and mobility measurements. II. Positive ion reactions of N+, O+, and N,+ with O2 and O+ with N, from thermal to N 2 eV. III. Negative ion reactions of O- with CO, NO, H, and Dz. (USA) This is a series of three articles by the authors. The first describes the apparatus and techniques used. A flow-drift tube was used with a buffer gas (usually helium) maintained through the tube by means of a Roots-type blower backed by a mechanical pump. Tube pressures were in the range 0.19-1.25 torr. The drift-reaction section was terminated by an ion detection system capable of mass analysis. The positive ion-molecule reactions N* + 0, -+ NO* + 0 or 02*+N, N,*+O,+O,*+N,, O*+O,-+O,*+O and 0* + Nz + NO* + N were measured with the above apparatus. The first four reactions were measured from thermal energy to about 2 eV ion kinetic energy in the centre of mass. The last reaction was measured from 0.3-3 eV ion kinetic energy. The data agrees well with previous results. The third paper describes a combined flowing afterglow-drift tube experimental apparatus which was used to measure the reaction rate constants as a function of ion kinetic energy for the reactions of O- with CO, NO, Hz and DZ. The reaction rates are discussed in some detail. M McFarland et al, J Chem Phys, 59 (12), 1973,661&6635. 40 146. Bethe surface, elastic and inelastic differential cross sections, Compton profile and binding effects for HZ obtained by electron scattering with 25 keV incident electrons. (USA) Electron impact spectra for Hz were obtained at scattering angles of l”, l.S”, 2”, 3”, 4”, So, 7” and 100” using 25 keV incident electrons.