Semiclassical treatment of atomhyphen;asymmetric rotor collisions; rotational excitation of formaldehyde at low energies

摘要

The formalism necessary for the application of ``classicalShyphen;matrix'' theory to collisions of an atom with a rigid asymmetric rotor is derived. This is applied to rotational excitation of formaldehyde by H2(taken to be spherically symmetric) at energies from 10 to 15deg;K. Classical Monte Carlo trajectory calculations were also carried out for the same system in the energy range 10ndash;40deg;K. The results support the proposal of Townes and Cheung that a collisional mechanism is responsible for the 111rarr;110anomalous absorption of formaldehyde in cool interstellar dust clouds.