Driven Morse oscillator: Classical chaos and quantum theory for two-frequency excitation

We extend our previous comparison of classical and quantum theories for the excitation and dissociation of a sinusoidally driven Morse oscillator [Phys. Rev. A 37, 796 (1988)] to the case of two-frequency driving. In both the classical and quantum theories the total threshold intensity for dissociation can be considerably smaller in the two-frequency case. This is consistent with results obtained with more artificial models of laser-driven molecular systems, and we provide an approximate resonance-overlap analysis to explain this trend. We also compare results obtained with adiabatic and sudden turn-on of the applied field, and comment on the use of absorbing boundaries for the computational identification of dissociation or ionization.