ENERGY AND PHASE RELAXATION ACCOMPANYING IMPULSIVE REACTIONS IN LIQUIDS

Experiments made possible by new laser methods explore ultrafast featu res of solution phase reaction dynamics. The results from two examples are given. Photodissociation of small molecules such as HgI2 and OCl- in solution yields highly excited vibrational state distributions and narrow bond length distributions. The dynamics in the transition stat e region and the ensuing dynamics can be followed by femtosecond laser experiments that probe the phase and energy loss processes. The mercu ric iodide experiments show that the phase relaxation is dominated by coherence transfer processes which have a strong analogy to classical motions. The population relaxation dynamics gives results similar to t hose from classical molecular dynamics simulations which suggest notwi thstanding the significant polarity of the molecules and solvents, tha t the relaxations are dominated by Lennard-Jones repulsion at sufficie ntly low frequencies.