Nonadiabatic dynamics between valence, nonvalence, and continuum electronic states in a heteropolycyclic aromatic hydrocarbon

Bull, James N. ORCID:, Anstöter, Cate S., Stockett, Mark H., Clarke, Connor J., Gibbard, Jemma A., Bieske, Evan J. and Verlet, Jan R. R. (2021) Nonadiabatic dynamics between valence, nonvalence, and continuum electronic states in a heteropolycyclic aromatic hydrocarbon. The Journal of Physical Chemistry Letters, 12 (49). 11811–11816. ISSN 1948-7185

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Internal conversion between valence-localized and dipole-bound states is thought to be a ubiquitous process in polar molecular anions, yet there is limited direct evidence. Here, photodetachment action spectroscopy and time-resolved photoelectron imaging with a heteropolycyclic aromatic hydrocarbon (hetero-PAH) anion, deprotonated 1-pyrenol, is used to demonstrate a subpicosecond (τ1 = 160 ± 20 fs) valence to dipole-bound state internal conversion following excitation of the origin transition of the first valence-localized excited state. The internal conversion dynamics are evident in the photoelectron spectra and in the photoelectron angular distributions (β2 values) as the electronic character of the excited state population changes from valence to nonvalence. The dipole-bound state subsequently decays through mode-specific vibrational autodetachment with a lifetime τ2 = 11 ± 2 ps. These internal conversion and autodetachment dynamics are likely common in molecular anions but difficult to fingerprint due to the transient existence of the dipole-bound state. Potential implications of the present excited state dynamics for interstellar hetero-PAH anion formation are discussed.

Item Type: Article
Additional Information: Funding Information: This work was undertaken as part of the STINT grant entitled “Unraveling the Interstellar Carbon Cycle with Action Spectroscopy”, funded by the Swedish Foundation for International Collaboration in Research and Higher Education (grant number PT2017-7328 to JNB and MHS). JNB acknowledges start-up funds from University of East Anglia. MHS acknowledges the Swedish Research Council (Grant No. 2016-03675) and the Carl Trygger Foundation (Grant No. 17:436). JAG is grateful for support from a Ramsay Memorial Fellowship. CJC is thankful for the supporting Durham Doctoral Scholarship. EJB acknowledges the Australian Research Council Discovery Project scheme (DP150101427 and DP160100474). JRRV acknowledges the European Research Council Starting Grant scheme (306536). Photodepletion experiments ( Supporting Information ) were performed in the laboratory of Prof. Steen Brøndsted Nielsen, Department of Physics, Aarhus University, Denmark. This article is in part based upon work from COST Action CA18212 – Molecular Dynamics in the GAS phase (MD-GAS), supported by COST (European Cooperation in Science and Technology). Electronic structure calculations were carried out on the High Performance Computing Cluster supported by the Research and Specialist Computing Support service at the University of East Anglia.
Uncontrolled Keywords: materials science(all),physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/2500
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
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Depositing User: LivePure Connector
Date Deposited: 03 Dec 2021 01:44
Last Modified: 09 Feb 2023 13:50
DOI: 10.1021/acs.jpclett.1c03532


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