Free-jet rotational spectrum and tunneling motion of difluoromethane...xenon

The rotational spectra of three isotopologues of difluoromethane...xenon have been investigated by free-jet millimeter-wave absorption spectroscopy. Only mu(c)-type transitions have been observed, all of them evenly split due to the internal motion of Xe relative to the difluoromethane moiety. The vibrational splitting, 39.1(3) MHz, has been used to estimate the tunneling barrier, V(2) = 109 cm(-1). Information on the dissociation energy has been deduced from centrifugal distortion effects (E(B) = 1.8 kJ mol(-1)). The xenon atom lies in the sigma(v) symmetry plane of difluoromethane containing the hydrogen atoms, at an r(0) distance of 3.816 A from its center of mass (cm), and forms a Xe-cm-C r(0) angle of 118 degrees . The observed conformation is in agreement with the minimum found with a distributed polarizability model.