Dipole moments of diatomic molecules

The effect of the presence of an electric field on the adiabatic approximation for a diatomic molecule is considered, and it is concluded that, to within experimental accuracy, the dipole moment can be calculated by averaging the "static" dipole moment over the molecular vibration. The variation of molecular dipole with vibrational excitation is investigated numerically, and, in an appendix, a possible inversion in relative vibrational absorption intensities is predicted.