title: Internal state thermometry of cold trapped molecular anions.
abstract: Photodetachment spectroscopy of OH(-) and H(3)O(2)(-) anions has been performed in a cryogenic 22-pole radiofrequency multipole trap. Measurements of the detachment cross section as a function of laser frequency near threshold have been analysed. Using this bound-free spectroscopy approach we could demonstrate rotational and vibrational cooling of the trapped anions by the buffer gas in the multipole trap. Below 50 K the OH(-) rotational temperature shows deviations from the buffer gas temperature, and possible causes for this are discussed. For H(3)O(2)(-) vibrational cooling of the lowest vibrational quantum states into the vibrational ground state is observed. Its photodetachment cross section near threshold is modelled with a Franck-Condon model, with a detachment threshold that is lower, but still in agreement with the expected threshold for this system.
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors.forename: Rico
authors.initials: R
authors.lastname: Otto
authors.forename: Alexander
authors.initials: A
authors.lastname: von Zastrow
authors.forename: Thorsten
authors.initials: T
authors.lastname: Best
authors.forename: Roland
authors.initials: R
authors.lastname: Wester