Excitation — Ionization and Excitation — Autoionization of Helium

Resonance effects in electron-impact ionization of helium

“…For a fixed scattering angle of 12 • and ejectedelectron angles of 60 • and 240 • , the coincidence signal is plotted as a function of the ejectedelectron energy in the vicinity of the (2s 2 ) 1 S auto-ionizing resonance at 33.24 eV. The results obtained in our first-order (RMPS-B1) and second-order (RMPS-B2) models are compared with the experimental data of McDonald and Crowe (1992) and also with the corresponding predictions of Marchalant et al (1997). Unfortunately, the background was subtracted from the published experimental data.…”

“…Data for the same resonances, but with improved energy resolution, were obtained by Crowe (1992, 1993) and by Crowe and McDonald (1993). Among others, Marchalant et al (1997) tried out their earlier secondorder model on these resonances and sometimes found very encouraging improvement in the agreement between theory and experiment when the second-order term was added. In particular, they provided additional evidence for the importance of the 'two-step mechanism' in the excitation of autoionization states, as suggested earlier by Godunov et al (1991) and also by Tweed (1992).…”

“…In order to provide a detailed view of the resonance profiles and to illustrate a possible sensitivity of the results to minor changes in the detection angle and the energy of the slow electron, figure 2 shows a three-dimensional plot of the RMPS-B2 predictions over the energy Crowe (1992); 'B1' and 'B2' refer to first-order and second-order models of this paper and that of Marchalant et al (1997), respectively. The two outgoing electrons are detected at angles of 12 • and 60 • /240 • , respectively.…”

Ethylene Epoxidation in a Low-Temperature Parallel Plate Dielectric Barrier Discharge System: Effect of Oxygen Source

“…It is worthwhile to point out that under the studied conditions of both the air and N 2 O systems, CO 2 was not detected and so all reactions to form CO 2 can be excluded. Most of the possible chemical pathways that may appear in the DBD system used in this study are proposed in eqs –, as previously reported. − …”

Ejected-electron spectroscopy of autoionizing resonances of helium excited by fast-electron impact

“…Therefore, besides further experimental studies, corresponding theoretical calculations are also absolutely essential. So far as we know, relative to the very few theoretical calculations about the DDCS of autoionization of He at low incident energy [19,36], many calculations have been developed for comparing and explaining the results of triple differential cross section (TDCS) of (e, 2e) experiments about autoionization of He, such as the first-order distorted-wave model [19,36,40], sixstate momentum space close-coupling approximation [41], and more sophisticated methods using the second-order theoretical model [33,34,[42][43][44][45]. While first-order models reach a fair agreement in some cases, the second-order models have performed better in most cases.…”