PUMP-PROBE SPECTROSCOPY OF PHOTOINDUCED CHARGE-TRANSFER REACTIONS IN SOLUTION

A theory of pump-probe spectroscopy of photoinduced charge separation processes in solution is developed. The pump-probe pathway is describe d by pump with excitation pulse which generates a nonstationary initia l state in the first excited state. This initial state evolves and tra nsfers to a second excited state (charge transfer state) nonadiabatica lly, and the system is probed by a second probe pulse. Doorway and win dow function approximations are used to separate these processes. Solu tion is treated as a continuum (Debye) model with one longitudinal rel axation time. Hence, after Wigner transformation of the time evolution of density matrix in Liouville space, the solvation dynamics of nonad iabatic charge separation processes obeys the semiclassical Zusman equ ation. Using the eigenfunction expansion method, we solve the bare abs orption spectrum numerically. An electronic coherence motion is observ ed in the overdamped exothermic invert regime. (C) 1997 American Insti tute of Physics.