Ultracold quantum dynamics:: Spin-polarized K+K2 collisions with three identical bosons or fermions -: art. no. 032722

We have developed a potential-energy surface for spin-polarized K(S-2)+K-2((3)Sigma(+)(u)) collisions and carried out quantum dynamical calculations of vibrational quenching at low and ultralow collision energies for both bosons K-39 and K-41 and fermions K-40. At collision energies above about 0.1 mK the quenching rates are well described by a classical Langevin model, but at lower energies a fully quantal treatment is essential. We find that for the low initial vibrational state considered here (v=1), the ultracold quenching rates are not substantially suppressed for fermionic atoms. For both bosons and fermions, vibrational quenching is much faster than elastic scattering in the ultralow-temperature regime. This contrasts with the situation found experimentally for molecules formed via Feshbach resonances in very high vibrational states.