Ph.D. Candidate: Matthew R. Ware
Research Advisor: Philip H. Bucksbaum
Date: Monday, February 25th, 2019
Location: PAB 102/103
Title: From time-resolved to frequency-resolved x-ray scattering
Gas-phase time-resolved x-ray scattering (TRXS) measures internuclear separations in a molecule following laser-induced photoexcitation. TRXS constitutes an indirect measurement of the molecular motion because it captures information in reciprocal-space and real-time, which then must be inverted to recover the charge density as it changes in time. The spatial resolution of the recovered charge density is fundamentally restricted by the x-ray wavelength used in the experiment. There is no corresponding technical restriction on the ability to scan the delay between the pump-laser pulse and the x-ray-probe pulses, and thus no lower limit on the ability to resolve beat frequencies from TRXS measurements. This observation motivates transforming the measured TRXS in reciprocal-space and real-time into its reciprocal-space and reciprocal-time representation through a temporal Fourier transform. The reciprocal-space and reciprocal-time representation, i.e. frequency-resolved x-ray scattering (FRXS), is a compact representation of the bound and dissociative motion of a molecule. FRXS may be used to segregate and identify modes of motion in a molecule, as well as measure key information about the identified states such as equilibrium positions, amplitude of motion, and beat frequencies for bound states, as well as initial positions and dissociation velocities for dissociative states.