Observing nuclear and electronic degrees of freedom simultaneously in a single ultrafast electron diffraction experiment

Jie Yang¹, Xiaolei Zhu², Todd J. Martinez³ and Xijie Wang<sup>4

 

1</sup>Department of Chemistry, Tsinghua University, China, jieyang.ued@gmail.com

²Department of Chemistry, Stanford University, USA, virtualzx@gmail.com

³Department of Chemistry, Stanford University, USA, todd.martinez@stanford.edu

⁴SLAC National Accelerator Laboratory, USA, wangxj@slac.stanford.edu

In nonadiabatic molecular dynamics, the complex interplay between nuclear and electronic degrees of freedom often dictates the reaction pathway and outcome. However, it has been challenging to record both electronic and nuclear dynamics simultaneously yet separately in a single experiment. Specifically, gas-phase ultrafast electron diffraction (GUED) has been considered as an experimental tool that is exclusively sensitive to the nuclear structural dynamics. In this presentation, we show that the functionality of GUED goes beyond the conventional scope—it can also track the electronic dynamics through inelastic electron scattering. In addition, the inelastic and elastic components are naturally separated in different scattering angles, thus the two sides of the dynamics are recorded separately in a single experiment. Using this method, we were able to record the nuclear-electronic interplay during the S₁S₀ internal conversion of pyridine molecule. This interpretation is fully supported by nonadiabatic ab initio molecular dynamics simulations using the ab initio multiple spawning approach.