Nonadiabatic wave packet dynamics and predissociation resonances in sodium hydride.

Vibrational wave packet dynamics provides an opportunity to explore the energy landscape and the population transfer between nonadiabatically coupled excited electronic states. Here the coupled nonadiabatic dynamics of the CΣ and DΣ states of sodium hydride (NaH) in the gas phase in the adiabatic picture is studied, using a sequence of ultra-fast laser pulses in the femtosecond region. Emergence of different population dynamics and dissociation probabilities is shown by carefully choosing the pulse wavelength, duration and time-shift between the pulses, exciting the molecule from the ground XΣ state the immediate AΣ state. Quantum dynamics simulations were performed in the adiabatic picture, avoiding the adiabatic to diabatic transformation. Predissociation resonances, vibrational states with finite lifetimes, arise due to nonadiabatic couplings between bound and continuum states. Here accurate resonance energies and widths are computed providing further insight into the dissociation dynamics.