This paper further investigates quantum activated rate theory from the viewpoint of quantum evolution operators. It is shown that a new adiabatic separation of the quantum system-bath Hamiltonian can, in a single time step, account for quantum turnover behavior at moderate temperatures, and it is also shown how this turnover exponentially vanishes at low temperatures. It is further shown that incorporation of nonadiabatic (interaction representation form) corrections produces quantitatively accurate results at low temperatures, thus extending the applicability of the interaction representation form of nonadiabatic corrections to adiabatic evolution operators.