Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuum

Bull, J.N.; West, C.W.; Verlet, J.R.R.

Abstract

Photoelectron velocity-map imaging and electronic structure calculations have been used to study the temporary anion (resonance) dynamics of the closed-shell site-specific deprotonated tetracene anion (C18H11−) in the hv = 3.26 eV (380 nm) to 4.13 eV (300 nm) range. In accord with a recent frequency-, angle-, and time-resolved photoelectron imaging study on a related but open-shell polyaromatic radical anion (Chem. Sci., 2015, 6, 1578–1589), population of π*-resonances situated in the detachment continuum efficiently recover the ground electronic state of the anion through ultrafast non-adiabatic dynamics, followed by characteristic statistical electron loss (thermionic emission). The combined electron yield of direct photodetachment and autodetachment from the optically-accessed resonances in C18H11− is several orders of magnitude smaller than thermionic emission from the ground electronic electronic state in the photon energy range studied. This result implies a resilience to prompt photoejection from UV radiation, and the ability of neutral PAH-like species to capture a free electron and form a long-lived molecular anion that ultimately decays by thermionic emission on a millisecond timescale. The attachment mechanism applies to polyaromatic species that cannot support dipole-bound states, and may provide an additional route to forming anions in astrochemical environments.

Citation

Bull, J., West, C., & Verlet, J. (2015). Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuum. Physical Chemistry Chemical Physics, 17(48), 32464-32471. https://doi.org/10.1039/c5cp05388a

• Journal Article Type: Article
• Acceptance Date: Nov 13, 2015
• Publication Date: Dec 28, 2015
• Deposit Date: Dec 18, 2015
• Publicly Available Date: Nov 13, 2016
• Journal: Physical Chemistry Chemical Physics
• Print ISSN: 1463-9076
• Electronic ISSN: 1463-9084
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 17
• Issue: 48
• Pages: 32464-32471
• DOI: https://doi.org/10.1039/c5cp05388a
• Public URL: https://durham-repository.worktribe.com/output/1396073