Detailed electron spectrometric study of the ionization of H2 by He* (21
S, 23
S) |
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Authors: | T Bregel A J Yencha M-W Ruf H Waibel H Hotop |
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Institution: | 1. Fachbereich Physik, Universit?t Kaiserslautern, D-6750, Kaiserslautern, Federal Republic of Germany
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Abstract: | The energy spectra of electrons released in thermal energy (≈ 50 meV) ionizing collisions of He*(21 S, 23 S) with H2 have been measured with high resolution and low background. Based on a detailed data analysis, we report accurate H 2 + (v′) vibrational populationsP(v′) for both He*(21 S)+H2(v′=0–10) and He*(23 S)+H2(v′=0–15) and the spectral shapeS(ε) for the individual vibrational peaks. The vibrational populationsP(v′) are quite similar to the Franck-Condon factorsf v ′0 for unperturbed H2(v″=0)→H 2 + (v′) transitions, but, more in detail, the ratiosP(v′)/f v ′0 show a characteristically differentv′-dependence for He*(23 S), He*(21 S), and HeIα(58.4 nm) ionization. The vibrational level separations in the He*(21 S, 23 S)+H2 spectra agree with those in the HeI photoelectron spectrum to within 1–2 meV. The spectral shapesS(ε) are characteristically different for He*(21 S)+H2 and He*(23 S)+H2, reflecting the respective differences in the entrance channel potentials, as determined previously in ab initio calculations and from scattering experiments. |
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