Nonlinear Dynamics of Chirped Pulse Excitation and Dissociation of Diatomic Molecules

The classical dynamics of a diatomic molecule modeled by a Morse oscillator interacting with a chirped infrared laser pulse is studied. When the chirping rate is small, the system can be described approximately in the moving frame by a time-independent Hamiltonian, which produces single-node separtrices (buckets) in phase space. Systems trapped in the buckets undergo convection to dissociation. This route to dissociation is different from the chaotic diffusion route for monochromatic excitation and requires a much lower threshold laser intensity to achieve dissociation.