Cargando…
Ultrafast dynamics of formation and autodetachment of a dipole-bound state in an open-shell π-stacked dimer anion
Isolated π-stacked dimer radical anions present the simplest model of an excess electron in a π-stacked environment. Here, frequency-, angle-, and time-resolved photoelectron imaging together with electronic structure calculations have been used to characterise the π-stacked coenzyme Q(0) dimer radi...
Autores principales: | , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Royal Society of Chemistry
2016
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6020752/ https://www.ncbi.nlm.nih.gov/pubmed/30155188 http://dx.doi.org/10.1039/c6sc01062h |
Sumario: | Isolated π-stacked dimer radical anions present the simplest model of an excess electron in a π-stacked environment. Here, frequency-, angle-, and time-resolved photoelectron imaging together with electronic structure calculations have been used to characterise the π-stacked coenzyme Q(0) dimer radical anion and its exited state dynamics. In the ground electronic state, the excess electron is localised on one monomer with a planar para-quinone ring, which is solvated by the second monomer in which carbonyl groups are bent out of the para-quinone ring plane. Through the π-stacking interaction, the dimer anion exhibits a number of charge-transfer (intermolecular) valence-localised resonances situated in the detachment continuum that undergo efficient internal conversion to a cluster dipole-bound state (DBS) on a ∼60 fs timescale. In turn, the DBS undergoes vibration-mediated autodetachment on a 2.0 ± 0.2 ps timescale. Experimental vibrational structure and supporting calculations assign the intermolecular dynamics to be facilitated by vibrational wagging modes of the carbonyl groups on the non-planar monomer. At photon energies ∼0.6–1.0 eV above the detachment threshold, a competition between photoexcitation of an intermolecular resonance leading to the DBS, and photoexcitation of an intramolecular resonance leading to monomer-like dynamics further illustrates the π-stacking specific dynamics. Overall, this study provides the first direct observation of both internal conversion of resonances into a DBS, and characterisation of a vibration-mediated autodetachment in real-time. |
---|