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

Bull, J. N. and West, C. W. and Verlet, J. R. R. (2015) 'Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuum.', Physical chemistry chemical physics., 17 (48). pp. 32464-32471.


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.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Date accepted:13 November 2015
Date deposited:18 January 2016
Date of first online publication:December 2015
Date first made open access:13 November 2016

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