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Title: Lifetime of weakly bound dimers of ultracold metastable helium studied by photoassociation

Abstract

We describe two-photon photoassociation (PA) experiments operated in an ultracold gas of metastable {sup 4}He{sup *} atoms in the 2 {sup 3}S{sub 1} state. Atom-molecule dark resonances as well as Raman signals provide information on the exotic molecule in the least bound vibrational J=2, v=14 state of the {sup 5}{sigma}{sub g}{sup +} interaction potential of two spin-polarized metastable atoms. The physical origin of the various two-photon PA signals is first discussed. Their linewidths are interpreted in terms of processes limiting the lifetime {tau} of the exotic molecule. A value of {tau}=1.4{+-}0.3 {mu}s is found, which significantly differs from two recent calculations of the Penning ionization rate induced by spin-dipole coupling [T. J. Beams et al., Phys. Rev. A 74, 014702 (2006); M. Portier and G. V. Shlyapnikov (unpublished)]. The limitation of {tau} by atom-molecule inelastic collisions is investigated and ruled out.

Authors:
; ; ;  [1];  [2]
  1. Ecole Normale Superieure, Laboratoire Kastler Brossel, 24 rue Lhomond, 75231 Paris Cedex 05 (France)
  2. (France)
Publication Date:
OSTI Identifier:
20982363
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.033415; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOM-MOLECULE COLLISIONS; DIMERS; DIPOLES; ELECTRONIC STRUCTURE; HELIUM; HELIUM 4; INELASTIC SCATTERING; LIFETIME; METASTABLE STATES; MOLECULES; MULTI-PHOTON PROCESSES; PHOTOIONIZATION; PHOTON-ATOM COLLISIONS; RAMAN SPECTRA; RESONANCE; SPIN; SPIN ORIENTATION; TEMPERATURE RANGE 0000-0013 K; VIBRATIONAL STATES

Citation Formats

Moal, S., Portier, M., Zahzam, N., Leduc, M., and Institut Francilien de Recherche sur les Atomes Froids, 24 rue Lhomond 75231 Paris Cedex 05. Lifetime of weakly bound dimers of ultracold metastable helium studied by photoassociation. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.033415.
Moal, S., Portier, M., Zahzam, N., Leduc, M., & Institut Francilien de Recherche sur les Atomes Froids, 24 rue Lhomond 75231 Paris Cedex 05. Lifetime of weakly bound dimers of ultracold metastable helium studied by photoassociation. United States. doi:10.1103/PHYSREVA.75.033415.
Moal, S., Portier, M., Zahzam, N., Leduc, M., and Institut Francilien de Recherche sur les Atomes Froids, 24 rue Lhomond 75231 Paris Cedex 05. Thu . "Lifetime of weakly bound dimers of ultracold metastable helium studied by photoassociation". United States. doi:10.1103/PHYSREVA.75.033415.
@article{osti_20982363,
title = {Lifetime of weakly bound dimers of ultracold metastable helium studied by photoassociation},
author = {Moal, S. and Portier, M. and Zahzam, N. and Leduc, M. and Institut Francilien de Recherche sur les Atomes Froids, 24 rue Lhomond 75231 Paris Cedex 05},
abstractNote = {We describe two-photon photoassociation (PA) experiments operated in an ultracold gas of metastable {sup 4}He{sup *} atoms in the 2 {sup 3}S{sub 1} state. Atom-molecule dark resonances as well as Raman signals provide information on the exotic molecule in the least bound vibrational J=2, v=14 state of the {sup 5}{sigma}{sub g}{sup +} interaction potential of two spin-polarized metastable atoms. The physical origin of the various two-photon PA signals is first discussed. Their linewidths are interpreted in terms of processes limiting the lifetime {tau} of the exotic molecule. A value of {tau}=1.4{+-}0.3 {mu}s is found, which significantly differs from two recent calculations of the Penning ionization rate induced by spin-dipole coupling [T. J. Beams et al., Phys. Rev. A 74, 014702 (2006); M. Portier and G. V. Shlyapnikov (unpublished)]. The limitation of {tau} by atom-molecule inelastic collisions is investigated and ruled out.},
doi = {10.1103/PHYSREVA.75.033415},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Photoassociation (PA) of ultracold metastable helium to the 2s2p manifold is theoretically investigated using a nonperturbative close-coupled treatment in which the laser coupling is evaluated without assuming the dipole approximation. The results are compared with our previous study [D. G. Cocks and I. B. Whittingham, Phys. Rev. A 80, 023417 (2009)], which makes use of the dipole approximation. The approximation is found to strongly affect the PA spectra because the photoassociated levels are weakly bound, and a similar impact is predicted to occur in other systems of a weakly bound nature. The inclusion of the approximation does not affect themore » resonance positions or widths; however, significant differences are observed in the background of the spectra and the maximum laser intensity at which resonances are discernible. Couplings not satisfying the dipole selection rule |J-1|{<=}J{sup '{<=}}|J+1| do not lead to observable resonances.« less
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  • We present high-precision trap loss spectroscopy of excited Na{sub 2} molecules obtained by the photoassociation of ultracold sodium atoms. Near the 3 {sup 2}S+3 {sup 2}P{sub 3/2} dissociation limit, hyperfine and rotational (Coriolis-type) interactions cause significant mixing of states of different nominal Hund's case (c) symmetry resulting in a complex pattern of spectral lines. We construct a theoretical model of the large, slowly rotating molecule starting from a long-range, atomic viewpoint. Interaction potentials are derived from the known long-range resonant dipole and van der Waals forces between atoms, supplemented at short range by the results of ab initio electronic-structure calculations.more » Spin-dependent interactions coupling the various angular momenta--nuclear spin, electron spin, electron orbit, and the mechanical rotation of the molecule as a whole--are derived from known atomic parameters. We avoid imposing approximate symmetries or coupling schemes and consequently include all nonadiabatic mixing of different degrees of freedom. Quantitative agreement between experiment and theory for both line positions and intensities is found. Specifically, we observe and calculate mixing of levels of 0{sub g}{sup -}, 0{sub u}{sup +}, and 1{sub g} symmetry bound by <50 GHz below the 3 {sup 2}S+3 {sup 2}P{sub 3/2} asymptote.« less
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