Bistability and chaos of laser‐driven molecules

Multiphoton vibrational excitation of molecules in contact with some dissipative mechanisms has been studied by analyzing a classical, semiclassical, and quantum model. Classical solutions of a driven damped Morse oscillator show bistable behavior for a wide range of damping constants, as laser intensity or frequency is adiabatically varied. In the case of a large damping constant and an intense field, period‐doubling bifurcations leading to chaotic solutions appear on both the upper and lower branches. Biustable behavior has also been found in analyzing a semiclassical model of Narducci, et al. But in this model instabilities have not been seen unless a field amplitude modulation was introduced. Both classical and semiclassical solutions show that the steady‐state values of the average vibrational coordinate (or energy) can be represented by a cusp catastrophe when plotted against laser intensity and frequency. A quantum mechanical study of a Morse oscillator coupled to a reservoir and driven by a classi...