Thermalization of fast cesium 5D{sub 3sol2} atoms in collisions with ground-state cesium atoms

Journal Article · Sat Jan 01 04:00:00 EST 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.71.012711· OSTI ID:20650240

Marks, A; Hickman, A P; Huennekens, J ^[1]; Streater, A D ^[2]

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1. Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)
2. Research Electro-Optics, 5505 Airport Boulevard, Boulder, Colorado 80301 (United States)

We have investigated collisions involving fast, excited Cs atoms produced by photodissociating Cs{sub 2} molecules with a pulsed dye laser. The velocities of the atoms in the 5D state formed by the process Cs{sub 2}(X {sup 1}{sigma}{sub g}{sup +})+({Dirac_h}/2{pi}){omega}{sub pump}{yields}Cs{sub 2}{sup *}{yields}Cs(5D)+Cs(6S) are much greater than typical thermal velocities associated with the cell temperature. Using a narrow-band cw probe laser to observe the increased Doppler broadening of the 5D{sub 3/2}{yields}5F{sub 5/2} excitation line shape, we are able to monitor the time evolution of the velocity distribution of these 5D atoms. We analyze the data using a model that predicts the time-dependent excitation line shape of the fast atoms. Because the photons used to dissociate the molecules have a well-defined energy, the velocity distribution of the excited atoms in the early time after they are produced can be fairly well determined. Over time, velocity-changing collisions with ground-state Cs atoms cause the velocity distribution of excited atoms to approach the thermal limit. An analysis based on the strong-collision model leads to a prediction that the observed line shape at intermediate times will be a linear combination of contributions from distinct 'fast' and 'thermalized' atomic populations. By fitting our data to this model, a rate coefficient for velocity-changing collisions of fast Cs(5D{sub 3/2}) atoms with ground-state Cs atoms has been determined. The result k{sub VCC}=(6.1{+-}1.2)x10{sup -10} cm{sup 3} s{sup -1} corresponds to an effective velocity-changing collision cross section of {sigma}{sub VCC}{sup Cs,eff}=(1.2{+-}0.2)x10{sup -14} cm{sup 2}.

• OSTI ID: 20650240
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 1 Vol. 71; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ATOM-ATOM COLLISIONS
ATOMS
CESIUM
CROSS SECTIONS
DISTRIBUTION
DOPPLER BROADENING
DYE LASERS
EXCITATION
EXCITED STATES
GROUND STATES
LASER RADIATION
MOLECULES
PHOTON-ATOM COLLISIONS
PHOTON-MOLECULE COLLISIONS
PHOTONS
THERMALIZATION
TIME DEPENDENCE
VELOCITY