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Lookup NU author(s): Dr Julien EngORCiD, Conor Rankine, Professor Thomas Penfold
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Owing to ring strain, cyclic ketones exhibit complex excited state dynamics with multiple competing photochemical channels active on the ultrafast timescale. While the excited state dynamics of cyclobutanone after π* ← n excitation into the lowest-energy excited singlet (S1) state has been extensively studied, the dynamics following 3s ← n excitation into the higher-lying singlet Rydberg (S2) state are less well understood. Herein, we employ fully quantum multiconfigurational time-dependent Hartree (MCTDH) simulations using a model Hamiltonian as well as “on-the-fly” trajectory-based surface-hopping dynamics (TSHD) simulations to study the relaxation dynamics of cyclobutanone following 3s ← n excitation and to predict the ultrafast electron diffraction scattering signature of these relaxation dynamics. Our MCTDH and TSHD simulations indicate that relaxation from the initially-populated singlet Rydberg (S2) state occurs on the timescale of a few hundreds of femtoseconds to a picosecond, consistent with the symmetry-forbidden nature of the state-to-state transition involved. There is no obvious involvement of excited triplet states within the timeframe of our simulations (<2 ps). After non-radiative relaxation to the electronic ground state (S0), vibrationally hot cyclobutanone has sufficient internal energy to form multiple fragmented products including C2H4+ CH2CO (C2; 20%) and C3H6 + CO (C3; 2.5%). We discuss the limitations of our MCTDH and TSHD simulations, how these may influence the excited state dynamics we observe, and—ultimately—the predictive power of the simulated experimental observable.
Author(s): Eng J, Rankine CD, Penfold TJ
Publication type: Article
Publication status: Published
Journal: Journal of Chemical Physics
Year: 2024
Volume: 160
Print publication date: 15/04/2024
Online publication date: 15/04/2024
Acceptance date: 28/03/2024
Date deposited: 15/04/2024
ISSN (print): 0021-9606
ISSN (electronic): 1089-7690
Publisher: AIP Publishing LLC
URL: https://doi.org/10.1063/5.0203597
DOI: 10.1063/5.0203597
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