Ultrafast valence to non-valence excited state dynamics in a common anionic chromophore.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31862884.
- Also identified by DOI 10.1038/s41467-019-13819-6 and PMC identifier 6925192.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Non-valence states in neutral molecules (Rydberg states) have well-established roles and importance in photochemistry, however, considerably less is known about the role of non-valence states in photo-induced processes in anions. Here, femtosecond time-resolved photoelectron imaging is used to show that photoexcitation of the S<sub>1</sub>(ππ*) state of the methyl ester of deprotonated para-coumaric acid - a model chromophore for photoactive yellow protein (PYP) - leads to a bifurcation of the excited state wavepacket. One part remains on the S<sub>1</sub>(ππ*) state forming a twisted intermediate, whilst a second part leads to the formation of a non-valence (dipole-bound) state. Both populations eventually decay independently by vibrational autodetachment. Valence-to-non-valence internal conversion has hitherto not been observed in the intramolecular photophysics of an isolated anion, raising questions into how common such processes might be, given that many anionic chromophores have bright valence states near the detachment threshold.