Rotational relaxation in ultracold CO+He collisions

Cold and ultracold collisions involving rotationally hot CO molecules were investigated by quantum mechanical coupled channel, coupled states, and potential scattering formulations. The quenching rate coefficients for initial rotational levels near the dissociation threshold were given. On comparing the stability of the CO "super rotors" against collisional decay with the investigations involving homonuclesr molecules it was found that the quasiresonant transitions provided a stronger contribution to the total relaxation rate than in the case of O₂. In the case of H₂, sharp structures in the distribution of total quenching rate coefficients were found at rotational levels where quasiresonant scattering was not allowed.