Rotational quenching of C2 with 3He and 4He collisions at ultracold temperatures

Abstract

Quantum mechanical closed coupling scattering calculations are carried out at temperatures ranging from K to 100 K for studying rotational transitions of C2 due to collisions with 3He and 4He employing our new C2-He potential energy surface computed at the CCSD(T)- F12b/aug-cc-pVQZ level of theory. Among the isotopes of He, the heavier 4He isotope has larger value of rotational quenching cross section than 3He isotope. Wigner’s threshold law holds below cm−1. Quenching rate coefficients suggest that C2 can be cooled with 4He buffer gas. The dominance of 4He on C2 molecule is further addressed by calculating the predissociation lifetime of C2.