Laser-intensity dependence of photoassociation in ultracold metastable helium

Cocks, Daniel G., and Whittingham, Ian B. (2009) Laser-intensity dependence of photoassociation in ultracold metastable helium. Physical Review A (Atomic, Molecular and Optical Physics), 80.

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Abstract

Photoassociation of spin-polarized metastable helium to the three lowest rovibrational levels of the J=1, 0<sub>u</sub><sup>+</sup> state asymptoting to 2s 3S1+2p 3P0 is studied using a second-order perturbative treatment of the line shifts valid for low laser intensities, and two variants of a nonperturbative close-coupled treatment, one based upon dressed states of the matter plus laser system, and the other on a modified radiative coupling which vanishes asymptotically, thus simulating experimental conditions. These nonperturbative treatments are valid for arbitrary laser intensities and yield the complete photoassociation resonance profile. Both variants give nearly identical results for the line shifts and widths of the resonances and show that their dependence upon laser intensity is very close to linear and quadratic, respectively, for the two lowest levels. The resonance profiles are superimposed upon a significant background loss, a feature for this metastable helium system not present in studies of photoassociation in other systems, which is due to the very shallow nature of the excited state 0<sub>u</sub><sup>+</sup> potential. The results for the line shifts from the close-coupled and perturbative calculations agree very closely at low laser intensities.

Item ID: 5212
Item Type: Article (Research - C1)
ISSN: 1094-1622
Keywords: atom-photon collisions, dressed states, metastable helium, spectral line shift, rotational-vibrational states, perturbation theory
Date Deposited: 09 Sep 2009 03:59
FoR Codes: 02 PHYSICAL SCIENCES > 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics > 020201 Atomic and Molecular Physics @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970101 Expanding Knowledge in the Mathematical Sciences @ 100%
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