Merged Beams Experiments for Mutual Neutralization Studies.
Molecular Physics seminar
Thursday 02 June 2016
to 11:00 at
Nathalie de Ruette (Atomic Physics Division)
Mutual Neutralization (MN) of anions and cations is a key reaction for the ionization balance in interstellar media :
A+ + B− → A + B. (1)
But so far, MN experimental studies have mainly been limited to collision energies down to a few eV and could not resolve the electronic (n), angular momentum (L), and spin (S) states, i.e. the LS-terms, of the neutral products [2,3].
We recently upgraded the merged beam setup in Louvain-la-Neuve to reach 5 meV collision energies, and incorporated three-dimensional momentum imaging using two position sensitive detectors. Besides providing clear coincidence signals between A and B, this technique gives unambiguous identification of LS-terms of the products via the measurement of the Kinetic Energy Release (KER).
We present absolute MN cross sections for N+ colliding with O− in the 0.005-10 eV energy range and KER-spectra at subthermal energies for C + on P− , C− , Si− , O− or S− , with identifications of the capture states of the products. While several of the A + + B − systems that we have studied give results well accounted for by means of simple multi-channel Landau-Zener calculations, there are striking exceptions for the C+ + O− and C+ + P− systems.
The present study will also serve to benchmark merged ion beams studies at the double electrostatic storage ring DESIREE now in operation at Stockholm University [4,5]. With DESIREE it will be possible to study MN between molecular ions with very low internal temperatures (down to 10 K).
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