Time‐Dependent quantum theory. IV. Effect of lattice relaxation on the optical spectra

Abstract

AbstractThe absorption and emission spectra of a diatomic “molecule” connected to an unstrained linear crystal are calculated for the circumstance where the diatomic undergoes a change of equilibrium internuclear separation in the electronic transition. The expansion (or contraction) of the diatomic results in a frequency dependent line‐width in the customary Lorentzian expression, and is manifested in the absorption spectrum as an asymmetric tailing to the blue, and in the emission spectrum as an asymmetric tailing to the red. The interaction of the diatomic with the lattice also produces a blue‐shift of the absorption spectrum and a red‐shift of the emission spectrum. An important consequence of the asymmetry is the apparent loss of integrated intensity of the line. The striking similarity, both in the width and the over‐all shape, of the emission line calculated here with those observed in the Vegard–Kaplan band of N2 dissolved in rare gas crystals is discussed.