München 2004 – scientific programme
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MO: Molekülphysik
MO 12: Poster I
MO 12.25: Poster
Tuesday, March 23, 2004, 14:00–16:00, Schellingstr. 3
Evidence for subthermal rotational populations in molecular ions through state-dependent Dissociative Recombination — •L. Lammich1, D. Strasser2, H. Kreckel1, M. Lange1, H.B. Pedersen1, V. Andrianarijaona1, S. Altevogt1, H. Buhr1, D. Schwalm1, A. Wolf1, and D. Zajfman2 — 1Max-Planck-Institut für Kernphysik, Heidelberg — 2Weizmann Institue of Science, Rehovot, Israel
Astrophysical applications and a clean theoretical understanding call for laboratory studies of electron–molecular ion interactions at cryogenic temperatures (10–100 K), while the ion storage rings commonly used for such measurements are large scale, room temperature devices. A recent experiment at the ion storage ring TSR indicates that subthermal rotational level populations of stored molecular ions have been prepared by continuous inelastic electron interactions.
Variations in the rate coefficient α for Dissociative Recombination of D2H+ ions with low energy electrons were observed over long storage times, and could be attributed to changes in the rotational level distributions of the stored ions. The comparison of data taken for different settings of the merged electron and ion beams show that, besides the coupling to the surrounding 300 K blackbody radiation, electron interactions can reduce the rotational excitations in the molecular ion beam. The latter was observed also for the radiatively inactive H3+ ion. Recent experimental results suggest in addition some influence of collisions with residual gas on the molecular rotations.
[1] L. Lammich et al., Phys. Rev. Lett. 91 (2003), 143201