title: Photodissociation of pyrrole-ammonia clusters by velocity map imaging: mechanism for the H-atom transfer reaction.
abstract: The photodissociation dynamics of pyrrole-ammonia clusters (PyH·(NH(3))(n), n = 2-6) has been studied using a combination of velocity map imaging and non-resonant detection of the NH(4)(NH(3))(n-1) products. The excited state hydrogen-atom transfer mechanism (ESHT) is evidenced through delayed ionization and presents a threshold around 236.6 nm, in agreement with previous reports. A high resolution determination of the kinetic energy distributions (KEDs) of the products reveals slow (∼0.15 eV) and structured distributions for all the ammonia cluster masses studied. The low values of the measured kinetic energy rule out the existence of a long-lived intermediate state, as it has been proposed previously. Instead, a direct N-H bond rupture, in the fashion of the photodissociation of bare pyrrole, is proposed. This assumption is supported by a careful analysis of the structure of the measured KEDs in terms of a discrete vibrational activity of the pyrrolyl co-fragment.
authors.affiliation: Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain. rubio@quim.ucm.es
authors.forename: L
authors.initials: L
authors.lastname: Rubio-Lago
authors.forename: G A
authors.initials: GA
authors.lastname: Amaral
authors.forename: A N
authors.initials: AN
authors.lastname: Oldani
authors.forename: J D
authors.initials: JD
authors.lastname: Rodríguez
authors.forename: M G
authors.initials: MG
authors.lastname: González
authors.forename: G A
authors.initials: GA
authors.lastname: Pino
authors.forename: L
authors.initials: L
authors.lastname: Bañares
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007700:Kinetics; D010782:Photolysis; D011758:Pyrroles / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D011758:Pyrroles; D000641:Ammonia; D006859:Hydrogen