DIABATIC ADIABATIC CHANNEL CORRELATION DIAGRAMS FOR 2 LINEAR ROTORS WITH LONG-RANGE DIPOLE-DIPOLE INTERACTION

Adiabatic und diabatic correlation diagrams, symmetry properties and patterns of adiabatic channel potential curves for two identical rotors with a long-range dipole-dipole interaction are investigated. Two features of such systems are analyzed. The first is related to an additional symmetry of the pure dipole-dipole interaction, which is invariant under the inversion of two rotors and which complements the usual invariance with respect to the total inversion. The second is related to a kind of ''hidden'' quasi-symmetry, which is connected to an approximate separability of variables for states with low values of the projection of the overall angular momentum of two rotors onto the line connecting the rotors. Due to these properties, the adiabatic channel potential curves exhibit many crossings and pseudocrossings. These features strongly modify the conventional correlation diagram based on the noncrossing rule for states of the same symmetry. Parameters which determine the nonadiabatic transition probabilities for low-lying states are calculated. Possible implications of the nonadiabatic coupling for systems with prevailing dipole-dipole interaction at long distances are discussed in connection with mechanisms of translational to rotational energy transfer in collisions of identical rotors.