DYNAMICS OF PHOTOCHEMICAL-REACTIONS STUDIED BY DEGENERATE 4-WAVE-MIXING

The scattering efficiency of a transient grating, i.e. the non-linear susceptibility chi(3) ( -omega; omega, -omega, omega), gives valuable information of the momentary state of the system. Here, chi(3) is first determined for the ground state and - after excitation of the molecule by ultrashort UV pulses - the subsequent states are investigated. As a first example of the technique, 3-hydroxyflavone in the ground state and the growth and decay of the proton transfer state are reported. The dispersion measured over the large frequency range from 10000 to 30000 cm-1 shows an enormous enhancement of approximately three orders of magnitude near resonances.