Prediction challenge: First principles simulation of the ultrafast electron diffraction spectrum of cyclobutanone

Jiří Suchan; Fangchun Liang; Andrew S Durden; Benjamin G Levine

doi:10.1063/5.0198333

Prediction challenge: First principles simulation of the ultrafast electron diffraction spectrum of cyclobutanone

J Chem Phys. 2024 Apr 7;160(13):134310. doi: 10.1063/5.0198333.

Authors

Jiří Suchan¹, Fangchun Liang^{1

2}, Andrew S Durden^{1

2}, Benjamin G Levine^{1

2}

Affiliations

¹ Institute of Advanced Computational Science, Stony Brook University, Stony Brook, New York 11794, USA.
² Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA.

PMID: 38573851
DOI: 10.1063/5.0198333

Abstract

Computer simulation has long been an essential partner of ultrafast experiments, allowing the assignment of microscopic mechanistic detail to low-dimensional spectroscopic data. However, the ability of theory to make a priori predictions of ultrafast experimental results is relatively untested. Herein, as a part of a community challenge, we attempt to predict the signal of an upcoming ultrafast photochemical experiment using state-of-the-art theory in the context of preexisting experimental data. Specifically, we employ ab initio Ehrenfest with collapse to a block mixed quantum-classical simulations to describe the real-time evolution of the electrons and nuclei of cyclobutanone following excitation to the 3s Rydberg state. The gas-phase ultrafast electron diffraction (GUED) signal is simulated for direct comparison to an upcoming experiment at the Stanford Linear Accelerator Laboratory. Following initial ring-opening, dissociation via two distinct channels is observed: the C3 dissociation channel, producing cyclopropane and CO, and the C2 channel, producing CH2CO and C2H4. Direct calculations of the GUED signal indicate how the ring-opened intermediate, the C2 products, and the C3 products can be discriminated in the GUED signal. We also report an a priori analysis of anticipated errors in our predictions: without knowledge of the experimental result, which features of the spectrum do we feel confident we have predicted correctly, and which might we have wrong?