Abstract

Ultrafast optical Kerr effect and photon echo experiments have shown that there is a correlation between the rates of simple chemical reactions and low frequency (10-100 cm^-1) librational modes present in polar solvents and proteins. However, no true microscopic identification of the relevant modes has been made, as these experiments are only sensitive to the equilibrium solvent spectrum. Time-resolved THz pump-probe spectroscopy may be more suitable, as it is in principle sensitive to the non-equilibrium dynamics of the solvent modes. We have developed a system for ultrafast visible/near-UV pump, THz-probe spectroscopy. Pump-probe experiments were performed on the carrier dynamics of photoexcited SI GaAs and the dynamic dipole solvation of two different dyes in polar solution.¹

© 1998 IEEE