Theory of time-resolved x-ray photoelectron diffraction from transient conformational molecules

Abstract

We formulate x-ray photoelectron diffraction (XPD) from molecules undergoing photochemical reactions induced by optical laser pulses, and then apply the formula to the simulation of time-dependent XPD profiles from both dissociating ${\mathrm{I}}_{2}$ molecules and bending $\mathrm{C}{\mathrm{S}}_{2}$ molecules. The dependence of nuclear wave-packet motions on the intensity and shape of the optical laser pulses is examined. As a result, the XPD simulations based on such nuclear wave-packet calculations are observed to exhibit characteristic features, which are compared with the XPD profiles due to classical trajectories of nuclear motions. The present study provides a methodology toward creating ``molecular movies'' of ultrafast photochemical reactions by means of femtosecond XPD with x-ray free-electron lasers.