Complex scattering lengths for ultracold He collisions with rotationally excited linear and nonlinear molecules

Journal Article · Mon Nov 15 00:00:00 EST 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.82.052711· OSTI ID:21528655

Benhui, Yang; Stancil, P C ^[1]; Forrey, R C ^[2]; Balakrishnan, N ^[3]

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1. Department of Physics and Astronomy and the Center for Simulational Physics, University of Georgia, Athens, Georgia 30602 (United States)
2. Department of Physics, Penn State University, Berks Campus, Reading, Pennsylvania 19610 (United States)
3. Department of Chemistry, University of Nevada Las Vegas, Las Vegas, Nevada 89154 (United States)

The translational and internal level cooling of atoms and molecules in ultracold gases results from a combination of elastic and inelastic collisional processes. While elastic collisions lead to rapid thermalization, exoergic inelastic collisions may lead to heating and trap loss. To date, most collisional studies have targeted low-lying levels of diatomic molecules. Here we investigate inelastic quenching and elastic scattering of rotationally excited linear (H{sub 2}, HD, CO, O{sub 2}, and CO{sub 2}) and nonlinear (H{sub 2}O and NH{sub 3}) molecules in ultracold collisions with He and report the corresponding complex scattering lengths. It has been found that the ratio of the imaginary component {beta} to the real component {alpha} of the scattering length generally increases with decreasing rotational constant for linear molecules. With the exception of CO, {beta} becomes significantly smaller than {alpha} as the energy gap for rotational transitions increases. In all cases, {beta} decreases with rotational energy gap for relatively large rotational excitation, allowing for convenient fits to an exponential energy gap formula. Excited rotational levels of H{sub 2} and HD appear to be collisionally stable due to the very low values of {beta}/{alpha}. Rotationally excited H{sub 2}O also appears to be a viable candidate for He buffer gas cooling due to relatively small values of {beta}.

• OSTI ID: 21528655
• Journal Information: Physical Review. A, Vol. 82, Issue 5; Other Information: DOI: 10.1103/PhysRevA.82.052711; (c) 2010 The American Physical Society; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
AMMONIA
ATOMS
CARBON DIOXIDE
CARBON MONOXIDE
COLLISIONS
COOLING
ELASTIC SCATTERING
ENERGY GAP
EXCITATION
HELIUM
HYDROGEN
MOLECULES
NONLINEAR PROBLEMS
OXYGEN
QUENCHING
SCATTERING LENGTHS
THERMALIZATION
WATER
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
DIMENSIONS
ELEMENTS
ENERGY-LEVEL TRANSITIONS
FLUIDS
GASES
HYDRIDES
HYDROGEN COMPOUNDS
LENGTH
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RARE GASES
SCATTERING
SLOWING-DOWN