title: Twisted Intramolecular Charge Transfer in Protonated Amino Pyridine.
abstract: The excited state properties of protonated ortho (2-), meta (3-), and para (4-) aminopyridine molecules have been investigated through UV photofragmentation spectroscopy and excited state coupled-cluster CC2 calculations. Cryogenic ion spectroscopy allows recording well-resolved vibronic spectroscopy that can be reproduced through Franck-Condon simulations of the ππ* local minimum of the excited state potential energy surface. The excited state lifetimes have also been measured through a pump-probe excitation scheme and compared to the estimated radiative lifetimes. Although protonated aminopyridines are rather simple aromatic molecules, their deactivation mechanisms are indeed quite complex with unexpected results. In protonated 3- and 4-aminopyridine, the fragmentation yield is negligible around the band origin, which implies the absence of internal conversion to the ground state. Besides, a twisted intramolecular charge transfer reaction is evidenced in protonated 4-aminopyridine around the band origin, while excited state proton transfer from the pyridinic nitrogen to the adjacent carbon atom opens with roughly 500 cm(-1) of excess energy.
authors.affiliation: Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay , F-91405 Orsay, France.|Centre Laser de l'Université Paris-Sud (CLUPS/LUMAT), Univ. Paris-Sud, CNRS, IOGS, Université Paris-Saclay , F-91405 Orsay, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Broquier
authors.affiliation: Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay , F-91405 Orsay, France.
authors.forename: Satchin
authors.initials: S
authors.lastname: Soorkia
authors.affiliation: CNRS, Aix-Marseille Université, PIIM UMR 7365, Avenue Escadrille Normandie-Niémen, 13397 Marseille Cedex 20, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Dedonder-Lardeux
authors.affiliation: CNRS, Aix-Marseille Université, PIIM UMR 7365, Avenue Escadrille Normandie-Niémen, 13397 Marseille Cedex 20, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Jouvet
authors.affiliation: CNRS, Aix-Marseille Université, PIIM UMR 7365, Avenue Escadrille Normandie-Niémen, 13397 Marseille Cedex 20, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Theulé
authors.affiliation: Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay , F-91405 Orsay, France.|Centre Laser de l'Université Paris-Sud (CLUPS/LUMAT), Univ. Paris-Sud, CNRS, IOGS, Université Paris-Saclay , F-91405 Orsay, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Grégoire