Autoionization of highly excited Rydberg states of diatomic molecules

Abstract

Autoionization due to the vibrational and/or rotational de-excitation of highly excited Rydberg states of diatomic molecules is investigated by using the multichannel quantum defect theory. In the two-channel approximation, an analytical expression for the decay width is obtained which is expressed in terms of the adiabatic quantum defects. A formula in the crude Born–Oppenheimer approximation can be derived as a simplification limit of the present formula. The crude Born–Oppenheimer approximation is shown to work in the case that the linearity holds well for the dependence of the adiabatic quantum defect on the internuclear distance, and that the vibrational quantum number of the initial Rydberg states is not large. The autoionization of H2 is investigated with use of the present formula and a comparison with the experimental data is made.