Quenching of internal rotations versus collisional cooling at ultralow energies for weakly interacting partners: Cs-2((3)Sigma(+)(u)) with He-3,He-4

Abstract

Quantum-scattering calculations at ultralow (close to 10(-6) cm(-1)) collision energies are carried out for the Cs dimer in its spin-stretched triplet state, interacting with helium. An ab initio potential energy surface is computed and employed, while the target molecule is kept in its ground vibrational state and several excitated initial rotational states are considered in the quantum dynamics. The highly anisotropic interaction is seen to cause, in spite of its weakness, internal energy quenching rates comparable with the efficiency of the collisional cooling of relative kinetic energies. The rates of spin-flip processes are also analyzed and compared with pure rotational quenching events.