Strong external field effects on electronic dephasing of molecular transitions in condensed media

We discuss the effects of a strong external field on the optical transition between two electronic states of a solute immersed in a medium. The solute states may be weakly or quite strongly coupled to the medium. The electron ic dephasing process is characterized via the power absorbed by the solute. The average absorbed power (P) over bar(t) for resonant, strong fields exh ibits an oscillatory decay in time, reflecting the finite change in the pop ulation difference of the electronic states, and the dephasing arising from the coupling to the medium. The coefficients of (P) over bar(t) depend on the detuning from resonance as well as the coupling strength between the ex ternal field and the solute's transition dipole. Our method is nonperturbat ive in the external field strength and shows that the spectral line shapes can be systematically altered by the application of a strong external field . We also show that for strong but off-resonance fields, (P) over bar(t) re turns to the linear response regime. (C) 1999 American Institute of Physics . [S0021-9606(99)51816-3].