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MO: Molekülphysik
MO 6: Dissociation and other Collision Processes
MO 6.4: Talk
Tuesday, April 3, 2001, 16:45–17:00, H1058
Dissociative Recombination of LiH+: Rate Coefficient and Final States — •S. Krohn1,2, M. Lange1, L. Knoll1, H. Kreckel1, J. Levin1, D. Schwalm1, R. Wester1, P. Witte2,1, A. Wolf1, and D. Zajfman2 — 1Max-Planck-Institut für Kernphysik, Heidelberg — 2Weizmann Institute of Science, 76100 Rehovot, Israel
LiH+, bound by only ∼0.12 eV, is considered to have initiated the lithium chemistry which crucially contributed to cooling and star formation in the early universe. The rate coefficient of its dissociative recombination (DR) in collisions with low-energy electrons (T∼300 K) is required in order to predict abundances of this species; while so far no measurements of the DR rate coefficient were available, a relatively low value (∼3× 10−8 cm3 s−1) was expected because neutral potential curves crossing the ionic potential seem to be absent. In the storage ring TSR we measured the rate coefficient of the reaction LiH++e→ Li(n)+ H(1s) for LiH+(v) ions relaxed to ∼300 K and analyzed the final states n. The decrease in storage lifetime of the LiH+ beam when merged with an electron beam at ∼12 meV average collision energy indicates a DR rate coefficient of (6±2)×10−7 cm3 s−1, much higher than expected. Imaging of the Li fragments indicated that predominantly final states with n≥6 are produced. For fragments with n≥8, field ionization points in the fringing regions of the TSR deflection field between the interaction region and the detector for Li+ ions could be determined. They reveal that the Li atoms predominatly produced are very highly excited (n=10–12). Supported by DIP(BMBF) and MINERVA.