Electronic and vibrational coherence effects in broadband transient absorption spectroscopy with chirped supercontinuum probing

The theory of transient absorption with chirped supercontinuum probing is developed for electronic excitation of a vibronic four-level scheme. Dephasing is modeled as homogeneous in the Bloch approximation together with inhomogeneous broadening. The time correction routine for transient spectra is shown to be identical to that of the nonresonant case which was treated previously. Contributions from sequential and coherent terms are calculated and compared to each other. The simulated data reveal how electronic and vibrational dephasing, detuning, and inhomogeneous broadening manifest themselves in the coherent component of femtosecond transient absorption spectra.