FEMTOSECOND REAL-TIME PROBING OF REACTIONS .15. TIME-DEPENDENT COHERENT ALIGNMENT

The time evolution of product-state anisotropy, through absorption or fluorescence, is developed and compared with the experimental observat ions for three reactions involving elementary and complex dynamics. Th e reactions are trans-stilbene-He --> trans-stilbene + He, ICN --> I CN, and HgI2 - HgI + I. Reagant rotation, applied torque, vibrational averaging, and dynamic axis switching are incorporated into the theor etical treatment. The theory is classical in approach, but it describe s the experimental behavior on the femtosecond to picosecond time scal e, which enables one to obtain the nature of the angular momentum in t he final distribution, the structure of the final fragments, and the g eometry of the initial complex prepared.