Optical paralysis in electronically congested systems: application to large-amplitude vibrational motion of ground state Na 2

Abstract

The possibility of using phase coherent optical pulse sequences to generate large-amplitude vibrational motion while locking excited state population has been demonstrated by us previously [Kosloff et al., Phys. Rev. Lett.69 (1992) 2172]. While the approach is compatible in principle with strong fields, in practice strong fields excite many higher electronic states and may produce multiphoton ionization, processes that are frequently neglected in model calculations. Here we demonstrate that it is possible to lock any number of unwanted electronic excitations by a single condition on the instantaneous phase of the pulse sequence. We call this scheme “optical paralysis”. Since only the phase of the field is determined by this condition, the amplitude of the field is still unspecified and can be chosen to achieve some desired objective, e.g. monotonic increase of the ground-state vibrational energy. The scheme is demonstrated by solving the time-dependent Schrödinger equation for nine coupled electronic states of Na 2, with energy deposited in the ground state and a single excited state while the population in all other excited states is kept locked.