Collisional Excitation of an Asymmetric Rotor, Silicon Dicarbide

We have computed rotational excitation rates from the asymmetric top molecule SiC2 in collisions with low-energy He atoms. The intermolecular forces were obtained from an electron gas model, and collision dynamics were treated within the infinite-order sudden approximation. Total excitation rates, i.e., summed over final levels, are expected to be accurate to ~50% and the larger state-to-state rates are likely to be within a factor of ~2 of the correct values, although some of the smaller (and less important) rates may be less accurate. These rates are also thought to reflect, within this level of accuracy, rates for excitation by collisions with H2 molecules.