Using time-dependent rate equations to describe chirped pulse excitation in condensed phases

A time-dependent rate equation formalism is developed to describe high-intensity excitation of molecules in condensed phases using broadband laser pulses. When electronic and vibrational dephasing rates are fast relative to the pulse dynamics, the generalized optical Bloch equations can be written as a set of coupled rate equations with coefficients that depend on the time-dependent overlap of the pulse spectrum with the molecular lineshape. These rate equations are shown to reproduce qualitatively the effects observed experimentally in recent quantum control experiments using high-intensity, chirped femtosecond pulsed excitation.