Extraction of potentials and dynamics from condensed phase pump-probe spectra: Application to I-2 in Kr matrices

The many-body dynamics in the condensed phase often leads to structureless absorption spectra while vibrational recurrences in localized coordinates a re preserved. A scheme is presented to directly extract anharmonicities and energy relaxation from the varying vibrational periods in pump-probe spect ra. For the B state of I-2 a constant anharmonicity and a vibrational energ y relaxation rate decreasing by one order of magnitude in the wavelength ra nge from 540 to 583 nm are obtained. An analytical expression for compensat ing the wave packet dispersion due to the anharmonicity is derived and it i s applied to the control of wave packets by chirped pulses. Focusing of the wave packet is experimentally observed in accordance with the anharmonicit y and even after significant energy relaxation. Predissociation rates are d etermined from the envelopes of the pump-probe spectra. (C) 1999 American I nstitute of Physics. [S0021-9606(99)01242-8].