Vibrational and rotational cooling of H{sub 3}{sup +}
- Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany)
- Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)
- Weizmann Institute of Science, 76100 Rehovot (Israel)
The vibrational relaxation of H{sub 3}{sup +} molecules from a conventional plasma ion source is studied performing Coulomb explosion imaging on the ions extracted from a storage ring after variable times of storage. Storage for 2 s is found sufficient for radiative relaxation of the breathing excitation and the fragment velocity distribution in the breathing coordinate then agrees well with simulations based on the calculated ground-state wave function. The radiative decay of the two lowest pure breathing levels (1,0{sup 0}) and (2,0{sup 0}) is seen to be considerably faster than expected from rotationless calculations. Assuming a high rotational excitation of the H{sub 3}{sup +} ions, as suggested already in earlier experiments, the theoretical transition probabilities of the University College London line list for H{sub 3}{sup +} [L. Neale, S. Miller, and J. Tennyson, Astrophys. J. 464, 516 (1996)] can explain the increase of the vibrational cooling rates and reproduce the observed decay curve for the lowest breathing-excited level, confirming the absolute transition probabilities of these line tables. The observations give evidence for a quasistable population of high-lying rotational levels in the stored ion beam, relevant for the interpretation of storage ring measurements on the rate coefficients for dissociative recombination of H{sub 3}{sup +} ions with low-energy electrons.
- OSTI ID:
- 20632288
- Journal Information:
- Physical Review. A, Vol. 66, Issue 5; Other Information: DOI: 10.1103/PhysRevA.66.052509; (c) 2002 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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