Signatures of electronic and nuclear coherences in ultrafast molecular x-ray and electron diffraction

Jérémy R Rouxel; Daniel Keefer; Shaul Mukamel

doi:10.1063/4.0000043

Signatures of electronic and nuclear coherences in ultrafast molecular x-ray and electron diffraction

Struct Dyn. 2021 Jan 11;8(1):014101. doi: 10.1063/4.0000043. eCollection 2021 Jan.

Authors

Jérémy R Rouxel¹, Daniel Keefer¹, Shaul Mukamel¹

Affiliation

¹ Department of Chemistry and of Physics and Astronomy, University of California, Irvine, California 92697-2025, USA.

Abstract

Femtosecond x-ray and electron diffraction hold promise to image the evolving structures of single molecules. We present a unified quantum-electrodynamical formulation of diffraction signals, based on the exact many-body nuclear + electronic wavefunction that can be extracted from quantum chemistry simulations. This gives a framework for analyzing various approximate molecular dynamics simulations. We show that the complete description of ultrafast diffraction signals contains interesting contributions involving mixed elastic and inelastic scattered photons that are usually masked by other larger contributions and are neglected. These terms include overlaps of nuclear wavepackets between different electronic states that provide an electronic decoherence mechanism and are important for the time-resolved imaging of conical intersections.