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

Abstract

We measure the ratio γ of the momentum transfer–to–vibrational quenching cross section for molecular thorium monoxide (ThO) [X([superscript 1]Σ[superscript +]), v = 1, J = 0] in collisions with atomic helium between 800 mK and 2.4 K. We find γ ∼ 10[superscript 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[subscript 3] = 8 ± 2 × 10[superscript −33] cm[superscript 6] s[superscript −1].