Spectral consequences of periodic orbit bifurcations of AB2 stretching vibrational modes

Analysis of the kinetically coupled Morse oscillator model of Thiele and Wilson is used to relate abrupt changes in the qualitative character of the stretching vibrational spectra of AB2 species to the loss of stability of the symmetric stretching periodic orbit above a certain energy threshold. A new uniform asymptotic solution of the relevant Hillʹs equation yields novel scaling relations that govern the dependence of the stability parameters on the mass ratio (mA/mB) and the reduced energy (E/D), scaled with respect to the dissociation energy. Crudely simulated dispersed emission spectra are used to illustrate the quantum mechanical consequences of the theory with particular reference to recent experiments on CS2.