Nonhyperbolic escape and changes in phase-space stability structures in laser-induced multiphoton dissociation of a...

The dependence of photodissociation of a diatomic molecule (vibrating according to the Morse potential) on the frequency of the laser field that induces it, is studied in the context of classical nonlinear dynamics. First, it is observed that as the laser frequency increases towards the harmonic frequency of the potential, a transition from stabilization due to Kolmogorov-Arnold-Moser tori to stabilization caused by the resonance stability island occurs. Then, considering the photodissociation as a nonhyperbolic half-scattering process, we investigate the influence of these changes in the phase space stability structures on dissociation dynamics via the examination of the fractal set of singularities appearing in the time-delay function of the initial state. It is found that the effective fractal dimension of this set (a finite-scale approximation of the exact dimension which is always equal to 1) and the percentage of its singularities provide a link between these changes and the dissociation rate.