Photoassociation of metastable helium

A. S. Dickinson; F. X. Gadéa; T. Leininger

doi:doi:10.1209/epl/i2004-10491-y

Europhys. Lett., 70 (3), pp. 320-326 (2005)
DOI: 10.1209/epl/i2004-10491-y

Photoassociation of metastable helium

A. S. Dickinson¹, F. X. Gadéa² and T. Leininger³

¹ School of Natural Sciences (Physics), University of Newcastle - Newcastle, NE1 7RU UK
² The Nano Science Group, CEMES, CNRS UPR 8011 29 rue J. Marvig, BP 4347, F-31055 Toulouse, France
³ Laboratoire de Physique Quantique, UMR 5626 du CNRS, Université Paul Sabatier 118 Route de Narbonne, F-31062 Toulouse Cedex 04, France

received 16 December 2004; accepted in final form 10 March 2005
published online 25 March 2005

Abstract
A theoretical study is performed for the photoassociation of metastable helium. Combining short-range, high-level, ab initio calculations for ${}^5\Sigma_{g/u}^+$ and ${}^5\Pi_{g/u}$ symmetries and long-range behaviour, better described in Hund's case (c), potential-energy curves for attractive, ${}^5\Sigma_{u}^+$ and ${}^5\Pi_{g}$ , as well as repulsive, ${}^5\Pi_{u}$ and ${}^5\Sigma_{g}^+$ , states of quintet metastable helium molecules dissociating to $2\,{}^3S+2\,{}^3P$ are obtained. Taking into account the atomic spin-orbit couplings, vibrational levels are derived for near-dissociation levels at the ³P₂ asymptote. Comparison with results from three recent photoassociation experiments obtained under different conditions ( $\mu$ K temperatures with spin alignment and mK temperatures without) allowed for an assignation of about three quarters of the observed levels. The robustness of the vibrational numbering is confirmed by testing a modification of the short-range potentials.

PACS
31.50.Df - Potential energy surfaces for excited electronic states.
32.80.Pj - Optical cooling of atoms; trapping.
33.20.Kf - Visible spectra.

© EDP Sciences 2005