Cold-atom–dimer reaction rates with He4, Li6,7 , and Na23

Abstract

Atom-dimer exchange and dissociation reaction rates are predicted for different combinations of two $^4$He atoms and one of the alkaline species among $^{6}$Li, $^{7}$Li and $^{23}$Na, by using three-body scattering formalism with short-range two-body interactions. Our study was concerned with low-energy reaction rates in which the $s-$, $p-$ and $d-$ wave contributions are the relevant ones. The $^4$He is chosen as one of the atoms in the binary mixture, in view of previous available investigations and laboratory accessibilities. Focusing on possible experimental cold-atom realizations with two-atomic mixtures, in which information on atom-dimer reaction rates can be extracted, we predict the occurrence of a dip in the elastic reaction rate for colliding energies smaller than 20 mK, when the dimer is the $^4$He$^{23}$Na molecule. We are also anticipating a zero in the elastic $p-$wave contribution for the $^4$He + $^4$He$^7$Li and $^4$He + $^4$He$^{23}$Na reaction processes. With weakly-bound molecules reacting with atoms at very low colliding energies, we interpret our results on the light of Efimov physics which supports model independence and robustness of our predictions. Specific sensitivities on the effective range were evidenced, highlighted by the particular inversion role of the $p-$ and $d-$waves in the atom exchange and dissociation processes.