Quenching vibrations of cesium dimers by He at low and ultralow temperatures: quantum dynamical calculations

This paper analyses in detail the energy redistribution from the upper vibrational levels of Cs dimers, thought to be obtained from initial recombination processes that generate excited internal states of the triplet configuration ³ Σ _u ⁺ . Their quenching is examined as they are made to further collide with ⁴He buffer gas at temperatures below and around 100 mK. The relevant cross sections are computed by using a multichannel quantum dynamical approach and employ a full, ab initio potential energy surface. Due to their smallness (see Ref. R.B. Ross, J.M. Powers, T. Atashroo, W.C. Ermler, I.A. LaJohn, P. Christiansen, J. Chem. Phys. 93, 6654 (1999)]) the fine structure effects have not been explicitly included in this study. The final, cumulative cross-sections are discussed and analyzed in terms of the overall quenching behavior shown by different initial states of the dimer and in terms of the changing ratios between collisional cooling and vibrational quenching cross sections as a function of trap temperature. The corresponding quenching rates are also computed and analysed.