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The photochemistry of Rydberg-excited cyclobutanone: Photoinduced processes and ground state dynamics

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 3sn 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 3sn 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.

Publication metadata

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


DOI: 10.1063/5.0203597


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Funder referenceFunder name
COSMOS Program Grant (Grant No. EP/X026973/1)
EPSRC Open Fellowship (Grant No. EP/W008009/1)