title: Multiscale excited state lifetimes of protonated dimethyl aminopyridines.
abstract: The excited state dynamics of protonated ortho (2-) and para (4-) dimethyl aminopyridine molecules (DMAPH(+)) has been studied through pump-probe photofragmentation spectroscopy and excited state coupled-cluster CC2 calculations. Multiscale temporal dynamics has been recorded over 9 orders of magnitude from subpicosecond to millisecond. The initially locally excited ππ* state rapidly decays within about 100 fs into a charge transfer state following 90° twist motion of the dimethyl amino group. While this twisted intramolecular charge transfer (TICT) state does not trigger any fragmentation, it selectively leads to specific two-color photofragments through absorption of the probe photon at 355 nm. Besides, the optically dark TICT state provides an efficient deactivation path with high intersystem probability to non-dissociative long-lived triplet states. Such a multiscale pump-probe photodissociation scheme paves the way to systematic studies of charge transfer reactions in the excited state of cold ionic systems stored in a cryogenic cooled ion trap and probed continuously up to the millisecond time scale.
authors.affiliation: Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Univ. Paris Sud, Université Paris-Saclay, F-91405 Orsay, France. gilles.gregoire@u-psud.fr.
authors.forename: Satchin
authors.initials: S
authors.lastname: Soorkia
authors.forename: Michel
authors.initials: M
authors.lastname: Broquier
authors.forename: Gilles
authors.initials: G
authors.lastname: Grégoire