Structural kinetics by stroboscopic gas electron diffraction Part 1. Time-dependent molecular intensities of dissociative states

Abstract

Theoretical analyses and model calculations are presented for the application of stroboscopic gas electron diffraction as a technique to study the structural kinetics of transient species in the femtosecond time domain. An expression for the time-dependent molecular diffraction intensities is developed and used to model the dynamics of the laser-induced dissociations of IBr and ICN. It is found taht the molecular intensities can be directly expressed in terms of the potential function of the dissociative state and other parameters that characterize the transient state dynamics. Thus, the solution of the inverse structural problem seems feasible, i.e. the determination of transient state parameters from time-dependent intensity data. In addition it is found that structural details of the dissociative processes can be time-resolved on a scale that is significantly faster than that of the electron probe pulse width. Our study indicates that, by measuring directly the evolution of transient state geometries, time-resolved electron diffraction provides a new type of information complementary to that obtained by spectroscopic techniques.