Mean lifetime measurements of HeH{sup 2+}(2{ital p}{sigma}) isotopes
- James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)
The HeH{sup 2+} molecular ion decays by an electronic dipole transition from its bound first excited state (2{ital p}{sigma}) to the repulsive ground state (1{ital s}{sigma}). We have calculated the mean lifetimes of the vibrational states of a few HeH{sup 2+} isotopes and found a large isotopic effect, in particular for highly excited vibrational states, i.e., states with the same {ital v} have different decay rates. The measured decay curves of {sup 4}HeH{sup 2+}, {sup 3}HeD{sup 2+}, and {sup 4}HeD{sup 2+} ( i.e., the number of HeH{sup 2+} molecular ions as a function of their flight time from the target cell where they were formed), in contrast, are similar to each other. The lack of a measurable isotopic effect is related to the HeH{sup 2+} creation mechanism. In the charge-stripping collisions, a distribution of vibrational states is populated by vertical transitions and is thus centered around roughly the same vibrational energy and not around the same quantum number {ital v}. The mean lifetimes of the different isotopes as a function of their energy are surprisingly similar to each other, therefore washing out the isotopic effect. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 285934
- Journal Information:
- Physical Review A, Journal Name: Physical Review A Journal Issue: 1 Vol. 54; ISSN 1050-2947; ISSN PLRAAN
- Country of Publication:
- United States
- Language:
- English
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