Photoelectron spectra of N{sub 2} +: Rotational line profiles studied with He;I{endash}excited angle-resolved spectroscopy and with synchrotron radiation
- Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala (Sweden)
- Lawrence Berkeley National Laboratory, University of California at Berkeley, Berkeley, California 94720 (United States)
We have recorded angle-resolved He I photoelectron spectra of the three outermost valence states in N{sub 2}{sup +}, with high enough resolution to observe rotational line profiles. For the two {Sigma} states, the X{sup 2}{Sigma}{sub g}{sup +} and the B{sup 2}{Sigma}{sub u}{sup +}, we found that the rotational branches corresponding to different changes in rotational quantum number can differ dramatically in {beta} value. The well-known difference in {beta} value for the {nu}=0 and {nu}=1 vibrations of the X{sup 2}{Sigma}{sub g}{sup +} state was found to be due to different rotational branching ratios and also different {beta} values of the rotational branches. For the {nu}=0{endash}2 vibrations of the A{sup 2}{Pi}{sub u} state, the {beta} value difference between rotational branches is much less pronounced than in the {ital X} and {ital B} states. We have also recorded synchrotron-radiation-excited photoelectron spectra of the {nu}=0 vibrational peaks of the X{sup 2}{Sigma}{sub g}{sup +} and B{sup 2}{Sigma}{sub u}{sup +} states where rotational line profiles are resolved. The intensities of the rotational branches were studied as function of photon energy, the {ital X} state between 23 and 65 eV, and the {ital B} state between 23 and 45 eV. The results for the X state have recently been presented in a Letter [G. {umlt O}hrwall, P. Baltzer, and J. Bozek, Phys. Rev. Lett. {bold 81}, 546, 1998]. The rotational branching ratios of the two states have very different behaviors as functions of photon energy. The relative intensities of the rotational branches in the {ital X} state change significantly over the studied energy range. The 3{sigma}{sub g}{r_arrow}k{sigma}{sub u} shape resonance apparently gives rise to a non-Franck-Condon-like behavior for the rotational branching ratio of the {ital X} state. In the {ital B} state, the rotational branching ratios remain essentially constant over the studied energy range. {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 328570
- Journal Information:
- Physical Review A, Journal Name: Physical Review A Journal Issue: 3 Vol. 59; ISSN 1050-2947; ISSN PLRAAN
- Country of Publication:
- United States
- Language:
- English
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