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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenSat, 13 Apr 2024 01:01:46 +0000Electron-impact excitation cross section for the two lowest triplet states of molecular hydrogen
https://resolver.caltech.edu/CaltechAUTHORS:CARpr67
Authors: {'items': [{'id': 'Cartwright-D-C', 'name': {'family': 'Cartwright', 'given': 'David C.'}}, {'id': 'Kuppermann-A', 'name': {'family': 'Kuppermann', 'given': 'Aron'}}]}
Year: 1967
DOI: 10.1103/PhysRev.163.86
Calculations for the electron-impact excitation cross sections of molecular hydrogen from its ground (X1Σg+) to its first (b3Σu+) and second (a3Σg+) triplet states were performed using the Ochkur (O) and Ochkur-Rudge (OR) approximations. All nuclear motions were taken into account. It was found that the first triplet cross section is sensitive to the choice of the ground-state wave function whereas the second one is not. The former is also sensitive to the excited-state wave function used. The results using the O approximation are significantly larger than those of the OR approximation, and the maximum cross section occurs at a somewhat lower energy. Use of the separated-atom approximation produced results significantly lower than those arising from inclusion of all the multicenter terms in the scattering amplitude. The sum of the first and second OR triplet cross sections agrees well with a recent approximate experimental determination of the cross section for the electron-impact dissociation of H2 into 2H. More accurate experiments are now needed to further test the OR approximation.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kpckz-4bn27Rearrangement Collisions: Effect of Core Terms, Nonorthogonality, and Conservation of Particle Flux on Approximate Theories
https://resolver.caltech.edu/CaltechAUTHORS:TRUpr68
Authors: {'items': [{'id': 'Truhlar-D-G', 'name': {'family': 'Truhlar', 'given': 'Donald G.'}}, {'id': 'Cartwright-D-C', 'name': {'family': 'Cartwright', 'given': 'David C.'}}, {'id': 'Kuppermann-A', 'name': {'family': 'Kuppermann', 'given': 'Aron'}}]}
Year: 1968
DOI: 10.1103/PhysRev.175.113
Several first-order methods for rearrangement collisions are compared by applying them all to the same problem: electron-exchange scattering off the hydrogen atom. The methods considered are Born-Oppenheimer (BO); Bates-Bassel-Gerjuoy-Mittleman (BBGM); and Ochkur (O) with its modifications by Rudge and Bely. Whenever possible, they are compared with close-coupling calculations or polarized-orbital calculations. The BO approximation gives better results if the core term is retained, indicating that this inclusion helps to achieve a cancellation of errors. The BBGM first-order method is found to give reasonable integral and differential cross sections at intermediate energies but not at low energies. The methods of Ochkur and Rudge give improved integral cross sections, but at low energies the differential cross sections may be poor. The unitarization procedure of Seaton and Bely is extended to calculate exchange scattering off neutral systems but only slightly improves the Ochkur-Rudge (OR) results. None of the methods examined is satisfactory in all regards. Several other improved methods are also reviewed.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/s5kek-fwb45Angular Dependence of Low-Energy Electron-Impact Excitation Cross Section of the Lowest Triplet States of H2
https://resolver.caltech.edu/CaltechAUTHORS:TRAjcp68
Authors: {'items': [{'id': 'Trajmar-S', 'name': {'family': 'Trajmar', 'given': 'S.'}}, {'id': 'Cartwright-D-C', 'name': {'family': 'Cartwright', 'given': 'D. C.'}}, {'id': 'Rice-J-K', 'name': {'family': 'Rice', 'given': 'J. K.'}}, {'id': 'Brinkmann-R-T', 'name': {'family': 'Brinkmann', 'given': 'R. T.'}}, {'id': 'Kuppermann-A', 'name': {'family': 'Kuppermann', 'given': 'A.'}}]}
Year: 1968
DOI: 10.1063/1.1670073
The differential cross sections for the electron-impact excitation of the lowest triplet states of molecular hydrogen (b3Sigmau+,a3Sigmag+) have been calculated from threshold to 85 eV impact energy using the Ochkur–Rudge theory. For the X1Sigmag+ --> b3Sigmau+ transition, the relative differential cross sections were measured with a low-energy, high-resolution electron-impact spectrometer from 10° to 80° scattering angle and impact energies of 25, 35, 40, 50, and 60 eV. Theory and experiment are in good agreement for the shape of the differential cross section for energies of 35 eV and above. However, at 25 eV, the theory continues to predict a rather well-developed maximum in the cross section at around 40° while the experimental cross sections are more isotropic. An appreciable contribution to the inelastic scattering in the energy loss region from 11 to 14 eV due to excitation to the a3Sigmag+ and/or c3Piu states is definitely established from the observed angular distributions. A quantitative evaluation of the individual angular behavior of the excitations in this region, however, would require a resolution higher than the presently available one of 0.030 eV.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/5w02x-hbm98Differential and integral cross sections for excitation of the 2(1)P state of helium by electron impact
https://resolver.caltech.edu/CaltechAUTHORS:TRUpra70
Authors: {'items': [{'id': 'Truhlar-D-G', 'name': {'family': 'Truhlar', 'given': 'Donald G.'}}, {'id': 'Rice-J-K', 'name': {'family': 'Rice', 'given': 'James K.'}}, {'id': 'Kuppermann-A', 'name': {'family': 'Kuppermann', 'given': 'Aron'}}, {'id': 'Trajmar-S', 'name': {'family': 'Trajmar', 'given': 'S.'}}, {'id': 'Cartwright-D-C', 'name': {'family': 'Cartwright', 'given': 'D. C.'}}]}
Year: 1970
DOI: 10.1103/PhysRevA.1.778
Differential scattering cross sections for excitation of helium by electron impact from its ground state to its 21P excited state have been measured at four incident electron energies in the range 26-55.5 eV for scattering angles between 10° and 70°, and at 81.6 eV for scattering angles between 10° and 80°. These differential cross sections have been placed on an absolute scale by normalizing them to the experimental absolute integral cross sections of Jobe and St. John. These experimental differential and integral cross sections have been compared with the results predicted by the Born approximation, and by several other first-order approximations in which direct excitation is calculated in the Born approximation and exchange scattering by various Ochkurlike approximations. The calculations provide reliable tests of these scattering theories since they are made using the accurate generalized oscillator strengths of Kim and Inokuti. As expected, these first-order theories are poor near threshold and exchange is important at high scattering angles for all energies. Further, the absolute magnitude of the calculated integral and small-angle differential cross sections is too large and is within 50% of experiment only at energies greater than 80 eV. These first-order models are in qualitative agreement with the experimental angular dependence at 34-81.6 eV for scattering angles between 10° and 40°. At higher scattering angles (corresponding to momentum transfers greater than about 1.6 a.u.), the calculated differential cross sections fall well below the experimental ones. The phase between the direct and exchange scattering amplitudes was found to be important at all energies, and is apparently not predicted correctly by any of the first-order models examined here. Some approximations for the exchange (e.g., Ochkur approximation and the post interaction form of the Ochkur-Rudge approximation) were found to be better for integral cross sections and some (e.g., prior Ochkur-Rudge approximation) were better for differential cross sections. The use of good analytic self-consistent-field (SCF) wave functions for both the ground and excited states was tested by computing generalized oscillator strengths from them and comparing these results with the calculations using the accurate generalized oscillator strengths. The SCF functions yield differential cross sections in quantitative disagreement (20%) with the accurate results, although the energy and angle dependence of the cross sections is predicted qualitatively correctly.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/32pg8-s9p48Group theoretical selection rules for electron-impact spectroscopy
https://resolver.caltech.edu/CaltechAUTHORS:20200221-112529321
Authors: {'items': [{'id': 'Goddard-W-A-III', 'name': {'family': 'Goddard', 'given': 'W. A., III'}, 'orcid': '0000-0003-0097-5716'}, {'id': 'Huestis-D-L', 'name': {'family': 'Huestis', 'given': 'D. L.'}}, {'id': 'Cartwright-D-C', 'name': {'family': 'Cartwright', 'given': 'D. C.'}}, {'id': 'Trajmar-S', 'name': {'family': 'Trajmar', 'given': 'Sandor'}}]}
Year: 1971
DOI: 10.1016/0009-2614(71)80499-2
Simple group theoretical principles are applied to the consideration of electron scattering off atoms and diatomic and polyatomic molecules. For all scattering angles Sg ↔ Su is forbidden for atoms. Fer axial scattering (0° or 180° scattering angle), Σ+ ⇹ Σ- for linear polyatomic molecules and Sg ⇹ Pg ⇹ Dg, etc., for atoms. This approach is also used to estimate relative strengths of electron-impact-induced transitions of diatomic and polyatomic molecules.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qa5d1-3mp58Theoretical and Experimental (Electron-Impact) Studies of the Low-Lying Rydberg States in O2
https://resolver.caltech.edu/CaltechAUTHORS:CARpra73
Authors: {'items': [{'id': 'Cartwright-D-C', 'name': {'family': 'Cartwright', 'given': 'David C.'}}, {'id': 'Hunt-W-J', 'name': {'family': 'Hunt', 'given': 'W. J.'}}, {'id': 'Williams-W', 'name': {'family': 'Williams', 'given': 'W.'}}, {'id': 'Trajmar-S', 'name': {'family': 'Trajmar', 'given': 'S.'}}, {'id': 'Goddard-W-A-III', 'name': {'family': 'Goddard', 'given': 'William A., III'}, 'orcid': '0000-0003-0097-5716'}]}
Year: 1973
DOI: 10.1103/PhysRevA.8.2436
Theoretical studies of the n=3,4,and 5 Rydberg series in O2, converging to O2+(X 2Πg), are presented and correlated with electron energy-loss spectra of molecular oxygen, in the region from 7.0 to 10.5 eV. The energy-loss spectra have been studied as a function of the scattering angle for a incident electron energy of 45 eV. The angular dependence determined for various features in the energy-loss spectra have been correlated with the known behavior for transitions between electronic states of certain symmetry, and with the theoretical results, to identify the low-lying Rydberg states. Four vibrational levels of the (3s σg) 3Πg Rydberg state have been observed superposed on top of the maximum intensity portion of the Schumann-Range continuum with T00=8.145±0.020 eV. The theoretical results, combined with the energy-loss measurements and the high-resolution photon-absorption work, lead to the assignment of the lowest dipole-allowed 3Σu- and 3Πu Rydberg states at T00≤9.31 eV and T00=9.97 eV, respectively.https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0t5p6-50d28