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The Journal of Chemical Physics

Time delays in cold elastic scattering

D. Field, Lars Bojer Madsen

Published Jan 9, 2003• 20 citations
Publisher

Abstract

Expressions are derived for time delays for elastic scattering in cold electron and cold atom collisions. Delays are found to occur in the femtosecond regime for virtual state electron scattering with CO2, using recent experimental data [Field et al., Phys. Rev. A 64, 22708 (2001)]. Delays associated with cold atom scattering may be of the order of 1 μs in the μK regime, using Li6 collisions as an example. The maximum theoretical time delay, obtained by magnetically tuning the scattering length, is found to have a universal value at any ultracold collision energy E, given by (2E)−1.

DOI
10.1063/1.1530584

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The elastic scattering properties for collisions between two 7 Li atoms are investigated in the cold and ultracold regimes separately. Based on recent theoretical and experimental results, we present the improved hybrid potentials for the singlet X 1 ∑ g + and triplet a 3 ∑ u + ground states of the Li 2 . Our calculated values for the scattering lengths a and the effective ranges r e are compared with previous ones and found them to be in good agreement. The scattering lengths are 34.6 a 0 for the singlet state and −27.6 a 0 for the triplet state. Shape resonances occur in the collisions at low energies. We also calculate the total cross sections and the energy positions of shape resonances for both X 1 ∑ g + and a 3 ∑ u + states.
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The elastic scattering properties of cold atoms are very sensitive to the details of the interatomic potentials.Based on recent theoretical and experimental investigations,the research presents improved hybrid potentials for the singletX1 ∑g+and tripleta3∑u+ground states of the6Li2by the cubic spline interpolation and extrapolation.The calculated values for the scattering lengths are compared with previous results,and good agreements are obtained.The scattering lengths are 36.5a0for the singlet state and-2138.74a0for the triplet state.
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