Rotational excitation of OH by H2at thermal energies

Using a recently computed potential energy surface, the authors calculate cross sections for the rotational excitation of OH by para-H 2 (in its rotational ground state) over the range of energies believed to be relevant to the interstellar OH emission. Results are obtained in Hund's case b coupling scheme (neglecting the spin-orbit interaction) and the significance of departures from case b coupling are considered. The authors results indicate that collisions with H 2 molecules may be expected to invert the populations of the ground rotational state and of certain excited-state Lambda doublets. At low temperatures (T