Use of electric fields to study nuclear spin conversion in molecules. Application to CH3F

The ortho-para nuclear spin conversion rate of gaseous 13CH3F molecules subjected to an external electric field has been calculated in the framework of intramolecular state mixing. Results are given for the mixing induced by the magnetic dipole-dipole interaction between the molecular nuclei. It is found that the Stark shift of the rotational levels can speed up the conversion rate by a few orders of magnitude at gas pressures appropriate to the experiment. Measurements of this effect will provide information about the role of state mixing in the conversion and the type of intramolecular interaction involved.