Mean lifetime of the bound 2{ital p}{sigma} state of HeH{sup 2+}

Journal Article · Tue Mar 01 04:00:00 EST 1994 · Physical Review A

DOI:https://doi.org/10.1103/PhysRevA.49.1774· OSTI ID:142631

Ben-Itzhak, I; Chen, Z; Esry, B D; Gertner, I; Heber, O; Lin, C D; Rosner, B ^[1]

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1. James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

Recently, experimental evidence for the existence of a bound state of the HeH{sup 2+} molecular ion was reported by Ben-Itzhak, Gertner, Heber, and Rosner [Phys. Rev. Lett. 71, 1347 (1993)]. This three-body system was predicted by Bates and Carson to have bound vibrational states in the 2{ital p}{sigma} electronic state despite the strong repulsion potential between the two nuclei. These 2{ital p}{sigma} vibrational states decay via an electronic transition to the 1{ital s}{sigma} repulsive ground state with a mean lifetime of about 1 nsec. We have used the ``fragment-fragment`` coincidence method to measure the mean lifetime of the HeH{sup 2+} molecular ions which dissociate in flight before reaching the detector. The yield of these molecular ions was measured as a function of the distance between the target cell and the analyzer exit. From this measurement a mean lifetime of 3.9{plus_minus}0.4 nsec was determined. The 2{ital p}{sigma}{r_arrow}1{ital s}{sigma} transition rates for all vibrational states have been calculated within the Born-Oppenheimer approximation using available oscillator strengths. It is shown that the transition rates decrease with increasing vibrational energy because of the ``stretch`` of the molecular ion. The distribution of 2{ital p}{sigma} vibrational states populated by vertical transitions from stripping the HeH{sup +} electronic ground state was evaluated, and the resulting decay curve compares well with the measured one.

• OSTI ID: 142631
• Journal Information: Physical Review A, Journal Name: Physical Review A Journal Issue: 3 Vol. 49; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CALCULATION METHODS
CATIONS
CHARGE STATES
HELIUM HYDRIDES
LIFETIME
MOLECULAR IONS