Ultracold chemistry with alkali-metal--rare-earth molecules

A first principles study of the dynamics of $^6$Li$(^2S)+^6$Li$^{174}$Yb$(^2\Sigma^+) \to ^6$Li$_2( ^1\Sigma^+)+^{174}$Yb$(^1S)$ reaction is presented at cold and ultracold temperatures. The computations involve determination and analytic fitting of a three-dimensional potential energy surface for the Li$_2$Yb system and quantum dynamics calculations of varying complexities, ranging from exact quantum dynamics within the close-coupling scheme, to statistical quantum treatment, and universal models. It is demonstrated that the two simplified methods yield zero-temperature limiting reaction rate coefficients in reasonable agreement with the full close-coupling calculations. The effect of the three-body term in the interaction potential is explored by comparing quantum dynamics results from a pairwise potential that neglects the three-body term to that derived from the full interaction potential. Inclusion of the three-body term in the close-coupling calculations was found to reduce the limiting rate coefficients by a factor of two.