Transfer of Rotational Energy in Molecular Collisions I. Elementary Processes Which Lead to Abnormal Rotation of the HgH Molecule

Abstract

By the application of photographic photometry, the intensity distribution within the HgH 4017 band excited by mercury-sensitized fluorescence has been studied as a function of the pressure of nitrogen and the pressure of water vapor present in the fluorescence tube. From the effect which the foreign gases exert on the observed distribution of molecules among rotational levels, conclusions are drawn regarding the transfers of energy which occur in collisions of the HgH molecule with metastable Hg atoms and with normal H2O and N2 molecules. The proportion of excited HgH molecules with rotational energy greater than 0.2 volt greatly exceeds the thermal value under all circumstances; the excess rotational energy has its source in the two following processes. In a collision between an unexcited HgH molecule and a metastable Hg atom, the excitation energy of the latter is sometimes taken up as both rotational and electronic energy of the HgH molecule. In a collision between a normal N2 molecule and a highly excited HgH molecule, part of the electronic and vibrational energy of the latter is converted into rotational energy.