X-Ray sum frequency generation; direct imaging of ultrafast electron dynamics

Abstract

X-ray diffraction from molecules in the ground state produces an image of their charge density, and time-resolved X-ray diffraction can thus monitor the motion of the nuclei. However, the density change of excited valence electrons upon optical excitation can barely be monitored with regular diffraction techniques due to the overwhelming background contribution of the core electrons. We present a nonlinear X-ray technique made possible by novel free electron laser sources, which provides a spatial electron density image of valence electron excitations. The technique, sum frequency generation carried out with a visible pump and a broadband X-ray diffraction pulse, yields snapshots of the transition charge densities, which represent the electron density variations upon optical excitation. The technique is illustrated by ab initio simulations of transition charge density imaging for the optically induced electronic dynamics in a donor/acceptor substituted stilbene.

References in corpus (9)

• X-ray diffraction from isolated and strongly aligned gas-phase molecules with a free-electron laser
• Ultrafast, ultrabright, X-ray holography using a uniformly-redundant array
• Imaging electronic quantum motion with light
• Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules
• Self-referenced coherent diffraction x-ray movie of Angstrom- and femtosecond-scale atomic motion
• Two-Dimensional Stimulated Resonance Raman Spectroscopy of Molecules with Broadband X-ray Pulses
• Opportunities for chiral discrimination using high harmonic generation in tailored laser fields
• Monitoring Nonadiabatic Avoided Crossing Dynamics in Molecules by Ultrafast X-Ray Diffraction
• Time-, Frequency-, and Wavevector-Resolved X-Ray Diffraction from Single Molecules

Cited by in corpus (6)

• Observation of strong nonlinear interactions in parametric down-conversion of x-rays into ultraviolet radiation
• Theory of nonlinear interactions between x rays and optical radiation in crystals
• A Laboratory Frame Density Matrix for Ultrafast Quantum Molecular Dynamics
• Simulations for x-ray imaging of wave-packet dynamics
• Microscopic electron dynamics in nonlinear optical response of solids
• Theory of parametric x-ray optical wavemixing processes