Abstract The behavior of dipole transition matrix elements between adiabatic eigenstates of diatomic molecules is explored in the region of large configuration mixing. It is demonstrated that the matrix element has a lorentzian shape as a function of internuclear distance. The effect of this shape on the spectrum of LiH is investigated. The strong enhancement of the dipole transition moment in the interaction region is suggested as a source for nonthermal population distributions and laser radiation in alkali diatomics and hydrides.