External-field effects on molecular electronic transitions in charge-transfer systems

Abstract

We investigate strong-external-field effects on optical transitions between electronic states of charge-transfer systems in condensed media. We will use as a model a two-level system coupled to a dissipative medium driven by a strong, time-dependent external field. The external field induces transitions between the levels, and the dissipation, represented by a stochastic process, induces relaxation. The power absorbed by the system is characterized by spectral densities that not only depend on the detuning from resonance and the strength of the dissipation, as found for line shapes in linear spectroscopy, but also on the strength of the external field. Our treatment is nonperturbative in the strength of the external field, and leads to the conclusion that spectral line shapes can be manipulated by the application of sufficiently strong external fields.