Slowing down of the relaxation of high-frequency gas polarization in a constant electric field

It is found that a sufficiently strong electric field can substantially dec rease the relaxation rate of high-frequency polarization of a gas correspon ding to the resonance dipole-dipole interaction of its molecules. The corre sponding decrease in the integrated cross section for intermolecular Weissk opf collisions is calculated using the two-level approximation for the desc ription of quantum dynamics of internal (vibrational) degrees of freedom of molecules, whereas their translational and rotational motions are treated classically. It is shown that the effect is caused by the Stark change of d ipole moments of molecules and the ordering of their orientations in a cons tant electric field. As a result, for a certain magnitude of this field, th e contributions of constant and high-frequency dipole moments of a molecule to the change in its density matrix upon a collision are counterbalanced t o a considerable extent. The conditions required for the experimental obser vation of the effect are formulated. (C) 2001 MAIK "Nauka/Interperiodica".