Semiclassical WUG corrections to the interaction energy of two coupled dipoles at low temperatures

Quantum corrections in the moderately low-temperature régime to the interaction potential energy of two permanent molecular dipoles are evaluated through the Wigner–Uhlenbeck–Gropper (WUG) semiclassical expansion of the density matrix, whose leading term is proportional to ℏ 2 , the dipoles being assumed in oscillatory motion around their position of minimum energy. Application of the resulting formulae to the ground states of a few heteropolar diatomic molecules and radicals shows that the quantum correction is not negligible, being particularly relevant for BH and OH.