Ultrafast Photochemistry and Electron Diffraction for Cyclobutanone in the S2 State: Surface Hopping with Time-Dependent Density Functional Theory

Ericka Roy Miller; Sean J. Hoehn; Abhijith Kumar; Dehua Jiang; Shane M. Parker

doi:10.1063/5.0203679

paper

Ultrafast Photochemistry and Electron Diffraction for Cyclobutanone in the S2 State: Surface Hopping with Time-Dependent Density Functional Theory

arXiv:2402.10336 · doi:10.1063/5.0203679

Abstract

We simulate the photodynamics of gas-phase cyclobutanone excited to the S $_{2}$ state using fewest switches surface hopping (FSSH) dynamics powered by time-dependent density functional theory (TDDFT). We predict a total C3+C2 photoproduct yield of 9%, with a C3:C2 product ratio of 1:8. Two primary S $_{2}$ $\to$ S $_{1}$ conical intersections are identified: $β$ stretch and CCH bend, with the higher energy $β$ stretch being associated with sub-picosecond S $_{2}$ decay. Excited state lifetimes computed with respect to electronic state populations were found to be 7.0 ps (S $_{2}$ $\to$ S $_{1}$ ) and 550 fs (S $_{1}$ $\to$ S $_{0}$ ). We also generate time-resolved difference pair distribution functions ( $Δ$ PDFs) from our TDDFT-FSSH dynamics results in order to generate direct comparisons to ultrafast electron diffraction experiment observables. Global and target analysis of time-resolved $Δ$ PDFs produced a distinct set of lifetimes: i) a 0.462 ps decay, and ii) a 16.8 ps decay that both resemble the S $_{2}$ minimum, as well as iii) a long ( $>$ nanosecond) decay that resembles the S $_{1}$ minimum geometry and the fully separated C3/C2 products. Finally, we contextualize our results by considering the impact of the most likely sources of significant errors.

arXiv comment10 pages, 9 figures, preprint before peer review

Ultrafast Photochemistry and Electron Diffraction for Cyclobutanone in the S2 State: Surface Hopping with Time-Dependent Density Functional Theory

Abstract

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