Femtosecond Time-resolved Optical Spectroscopy Research Articles

Femtosecond spectroscopy of ultrafast nonadiabatic excited-state dynamics on the basis of ab initio potential-energy surfaces: the S2 state of pyrazine

A theoretical description of femtosecond time-resolved optical spectroscopy of isolated polyatomic molecules is outlined. Our ultimate goal is the characterization of the system response on a microscopic level, that is, time-dependent quantum dynamics. Employing a simplified model Hamiltonian which includes the most relevant electronic states and vibrational modes, the intramolecular quantum dynamics is treated numerically exactly. The model Hamiltonian is constructed, via a Taylor expansion in terms of ground-state normal coordinates, from ab initio potential-energy surfaces. Additional phase relaxation effects (optical pure dephasing) due to weakly coupled modes have been included in a phenomenological manner using the density-matrix formalism