A five-dimensional potential-energy surface for the rotational excitation of SO2 by H2 at low temperatures.

The SO(2) molecule is detected in a large variety of astronomical objects, notably molecular clouds and star-forming regions. An accurate modeling of the observations needs a very good knowledge of the collisional excitation rates with H(2) because of competition between collisional and radiative processes that excite and quench the different rotational levels of SO(2). We report here a five-dimensional, rigid-body, interaction potential for SO(2)-H(2). As a first application, we present rate constants for excitation/de-excitation of the 31 first levels of SO(2) by para-H(2) at low temperatures. Propensity rules are discussed.