Vacuum Ultraviolet Excited State Dynamics of the Smallest Ketone: Acetone

Ruaridh Forbes; Simon P Neville; Martin A B Larsen; Anja Röder; Andrey E Boguslavskiy; Rune Lausten; Michael S Schuurman; Albert Stolow

doi:10.1021/acs.jpclett.1c02612

Vacuum Ultraviolet Excited State Dynamics of the Smallest Ketone: Acetone

J Phys Chem Lett. 2021 Sep 9;12(35):8541-8547. doi: 10.1021/acs.jpclett.1c02612. Epub 2021 Aug 31.

Authors

Ruaridh Forbes^{1

2

3}, Simon P Neville⁴, Martin A B Larsen⁵, Anja Röder⁶, Andrey E Boguslavskiy², Rune Lausten⁴, Michael S Schuurman^{4

6}, Albert Stolow^{2

4

6

7}

Affiliations

¹ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, U.K.
² Department of Physics, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada.
³ Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
⁴ National Research Council of Canada, Ottawa, ON K1A 0R6, Canada.
⁵ Department of Chemistry, University of Copenhagen, 2100 Copenhagen ø, Denmark.
⁶ Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis Pasteur Pvt, Ottawa, ON K1N 6N5, Canada.
⁷ Joint Centre for Extreme Photonics, University of Ottawa - National Research Council, Ottawa, ON K1N 5A2, Canada.

PMID: 34464141
DOI: 10.1021/acs.jpclett.1c02612

Abstract

We combined tunable vacuum-ultraviolet time-resolved photoelectron spectroscopy (VUV-TRPES) with high-level quantum dynamics simulations to disentangle multistate Rydberg-valence dynamics in acetone. A femtosecond 8.09 eV pump pulse was tuned to the sharp origin of the A₁(n3d_yz) band. The ensuing dynamics were tracked with a femtosecond 6.18 eV probe pulse, permitting TRPES of multiple excited Rydberg and valence states. Quantum dynamics simulations reveal coherent multistate Rydberg-valence dynamics, precluding simple kinetic modeling of the TRPES spectrum. Unambiguous assignment of all involved Rydberg states was enabled via the simulation of their photoelectron spectra. The A₁(ππ*) state, although strongly participating, is likely undetectable with probe photon energies ≤8 eV and a key intermediate, the A₂(nπ*) state, is detected here for the first time. Our dynamics modeling rationalizes the temporal behavior of all photoelectron transients, allowing us to propose a mechanism for VUV-excited dynamics in acetone which confers a key role to the A₂(nπ*) state.