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Exotic helium molecules; Molecules exotiques d'helium

Abstract

We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} =  More>>
Authors:
Publication Date:
Dec 15, 2007
Product Type:
Thesis/Dissertation
Report Number:
FRNC-TH-7439
Resource Relation:
Other Information: TH: These physique quantique; 186 refs.; Also available from BIUS Jussieu - Service des theses, Batiment F - Mezzanine - Boite courrier 58, 4 place Jussieu, 75252 - Paris Cedex 05 (France)
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOM-ATOM COLLISIONS; AUTOIONIZATION; HELIUM; METASTABLE STATES; PENNING EFFECT
OSTI ID:
21124652
Research Organizations:
Paris-6 Univ., Ecole Normale Superieure, Dept. de Physique, Lab. Kastler Brossel, 75 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR0801528007376
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
213 pages
Announcement Date:
Feb 26, 2009

Citation Formats

Portier, M. Exotic helium molecules; Molecules exotiques d'helium. France: N. p., 2007. Web.
Portier, M. Exotic helium molecules; Molecules exotiques d'helium. France.
Portier, M. 2007. "Exotic helium molecules; Molecules exotiques d'helium." France.
@misc{etde_21124652,
title = {Exotic helium molecules; Molecules exotiques d'helium}
author = {Portier, M}
abstractNote = {We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)}
place = {France}
year = {2007}
month = {Dec}
}