Origin of Spectral-Line Satellites

Abstract

It is pointed out that the phenomenon of satellites of spectral lines is attributable to the breakdown of the Born-Oppenheimer approximation in the upper state of the collision-pair molecule owing to the proximity or crossing of molecular potential curves of the same symmetry. The Fano treatment of the configuration interaction between a single bound level and a continuum in conjunction with certain simple models for the potential curves yields an analytical expression for the intensity in the near wing of the spectral lines. The distant blue satellites may be shown to arise from the interaction with a second bound vibrational level. Combinations and variations of these two possibilities lead to cases typical of those which have been observed.