Vibrational quenching of the electronic ground state in ThO in cold collisions with 3He

Abstract

We measure the ratio γ of the momentum transfer–to–vibrational quenching cross section for molecular thorium monoxide (ThO) [ X ( 1 Σ + ) , v = 1 , J = 0 ] in collisions with atomic helium between 800 mK and 2.4 K. We find γ ∼ 10 4 . We also observe indirect evidence for ThO-He van der Waals complex formation, which has been predicted by theory [Tscherbul, Sayfutyarova, Buchachenko, and Dalgarno, J. Chem. Phys. 134, 144301 (2011)], and in conjunction, we determine the three-body recombination rate constant at 2.4 K, Γ 3 = 8 ± 2 × 10 − 33

cm 6

s − 1 .