Monitoring the evolution of relative product populations at early times during a photochemical reaction

Identifying multiple rival reaction products and transient species formed during ultrafast photochemical reactions and determining their time-evolving relative populations are key steps towards understanding and predicting photochemical outcomes. Yet, most contemporary ultrafast studies struggle with clearly identifying and quantifying competing molecular structures/species amongst the emerging reaction products. Here, we show that mega-electronvolt ultrafast electron diffraction in combination with ab initio molecular dynamics calculations offers a unique route to determine time-resolved populations of the various isomeric products formed after UV (266 nm) excitation of the five-membered heterocyclic molecule thiophenone. This strategy reveals an unexpectedly high (~50%) yield of an episulfide isomer containing a strained 3-membered ring within ~1 ps at early times and rapid interconversions between the rival photoproducts.Trajectory dataset: xyz files can be opened with a text editor or a molecular visualizer (VMD).Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: PHYS1753324Funding provided by: U.S. Department of EnergyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000015Award Number: DE-AC02-05-CH11231Funding provided by: U.S. Department of EnergyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000015Award Number: DE-AC02-76SF00515Funding provided by: U.S. Department of EnergyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000015Award Number: DE-FG02-86ER13491Funding provided by: U.S. Department of EnergyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000015Award Number: DE-SC0019451Funding provided by: U.S. Department of EnergyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000015Award Number: DE-SC0017995Funding provided by: U.S. Department of EnergyCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000015Award Number: DE-SC0020276Funding provided by: Horizon 2020 Framework ProgrammeCrossref Funder Registry ID: http://dx.doi.org/10.13039/100010661Award Number: 803718Funding provided by: Engineering and Physical Sciences Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000266Award Number: EP/V026690/1Funding provided by: Australian Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000923Award Number: DE200100549Funding provided by: Engineering and Physical Sciences Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000266Award Number: EP/L005913/1Funding provided by: Engineering and Physical Sciences Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000266Award Number: EP/R513039/1Funding provided by: Agence Nationale de la RechercheCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001665Award Number: ANR-20-CE29-0014UED dataset: raw data of the 15uJ experiment discussed in the main text. Trajectory dataset: xyz trajectories of the dynamics discussed in the main text. See supplementary material for the details of the collection