Nonadiabatic Dynamics between Valence, Nonvalence, and Continuum Electronic States in a Heteropolycyclic Aromatic Hydrocarbon

Bull, James N.; Anstöter, Cate S.; Stockett, Mark H.; Clarke, Connor J.; Gibbard, Jemma A.; Bieske, Evan J.; Verlet, Jan R.R.

Abstract

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.

Citation

Bull, J. N., Anstöter, C. S., Stockett, M. H., Clarke, C. J., Gibbard, J. A., Bieske, E. J., & Verlet, J. R. (2021). Nonadiabatic Dynamics between Valence, Nonvalence, and Continuum Electronic States in a Heteropolycyclic Aromatic Hydrocarbon. Journal of Physical Chemistry Letters, 12(49), 11811-11816. https://doi.org/10.1021/acs.jpclett.1c03532

• Journal Article Type: Article
• Acceptance Date: Dec 1, 2021
• Online Publication Date: Dec 6, 2021
• Publication Date: Dec 16, 2021
• Deposit Date: Jan 11, 2022
• Publicly Available Date: Dec 6, 2022
• Journal: Journal of Physical Chemistry Letters
• Electronic ISSN: 1948-7185
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 12
• Issue: 49
• Pages: 11811-11816
• DOI: https://doi.org/10.1021/acs.jpclett.1c03532
• Public URL: https://durham-repository.worktribe.com/output/1218210