title: Biradicalic excited states of zwitterionic phenol-ammonia clusters.
abstract: Phenol-ammonia clusters with more than five ammonia molecules are proton transferred species in the ground state. In the present work, the excited states of these zwitterionic clusters have been studied experimentally with two-color pump probe methods on the nanosecond time scale and by ab initio electronic-structure calculations. The experiments reveal the existence of a long-lived excited electronic state with a lifetime in the 50-100 ns range, much longer than the excited state lifetime of bare phenol and small clusters of phenol with ammonia. The ab initio calculations indicate that this long-lived excited state corresponds to a biradicalic system, consisting of a phenoxy radical that is hydrogen bonded to a hydrogenated ammonia cluster. The biradical is formed from the locally excited state of the phenolate anion via an electron transfer process, which neutralizes the charge separation of the ground state zwitterion.
authors.affiliation: University of Buenos Aires, Ciudad Universitaria, 3er piso, Pab. II, 1428 Buenos Aires, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Carrera
authors.forename: I B
authors.initials: IB
authors.lastname: Nielsen
authors.forename: P
authors.initials: P
authors.lastname: Carçabal
authors.forename: C
authors.initials: C
authors.lastname: Dedonder
authors.forename: M
authors.initials: M
authors.lastname: Broquier
authors.forename: C
authors.initials: C
authors.lastname: Jouvet
authors.forename: W
authors.initials: W
authors.lastname: Domcke
authors.forename: A L
authors.initials: AL
authors.lastname: Sobolewski