Multichannel Cold Collisions between Metastable Sr Atoms

Abstract

We present a multichannel-scattering calculation of elastic and inelastic cold collisions between two low-field seeking, metastable ${}^{\mathrm{88}}\mathrm{S}\mathrm{r}$ [$(5s5p){}^{3}P_2$] atoms in the presence of an external magnetic field. The scattering physics is governed by strong anisotropic long-range interactions, which lead to pronounced coupling among the partial waves of relative motion. As a result, nonadiabatic transitions are shown to trigger a high rate of inelastic losses. At relatively high energies, $T>100\mu \mathrm{K}$, the total inelastic collision rate is comparable with the elastic rate. However, at lower collisional energy, the elastic rate decreases, and at $T\sim 1\mu \mathrm{K}$, it becomes substantially smaller than the inelastic rate. Our study suggests that magnetic trapping and evaporative cooling of ${}^{\mathrm{88}}\mathrm{S}\mathrm{r}$ [$(5s5p){}^{3}P_2$] atoms, as well as ${}^{\mathrm{40}}\mathrm{C}\mathrm{a}$ [$(4s4p){}^{3}P_2$], in low-field seeking states will prove difficult to achieve experimentally.