MOLECULAR-TRANSITION STATE, RESONANCES, AND PERIODIC-ORBIT THEORY

The dynamics of the molecular transition state, in a reaction or photo dissociation process, may be analyzed by semiclassical methods. We inv estigate the classical dynamics of the transition state in the dissoci ation HgI2(X (1) Sigma(g)(+))-->(HgI)-Hg-hv(X (2) Sigma(+))+I, and app ly the semiclassical quantization methods based on periodic-orbit theo ry. A series of resonances is characterized in a low-energy regime, wh ere the classical dynamics is regular, and at high energies, after a t ransition to chaos has occurred. In a complementary fashion, we analyz e the quantum-mechanical propagation of wave packets. The spectrum whi ch is derived from the quantum-mechanical autocorrelation function is compared with the semiclassical results.