title: Hexapole-Oriented Asymmetric-Top Molecules and Their Stereodirectional Photodissociation Dynamics.
abstract: Molecular orientation is a fundamental requisite in the study of stereodirected dynamics of collisional and photoinitiated processes. In this past decade, variable hexapolar electric filters have been developed and employed for the rotational-state selection and the alignment of molecules of increasing complexity, for which the main difficulties are their mass, their low symmetry, and the very dense rotational manifold. In this work, for the first time, a complex molecule such as 2-bromobutane, an asymmetric top containing a heavy atom (the bromine), was successfully oriented by a weak homogeneous field placed downstream from the hexapolar filter. Efficiency of the orientation was characterized experimentally, by combining time-of-flight measurements and a slice-ion-imaging detection technique. The application is described to the photodissociation dynamics of the oriented 2-bromobutane, which was carried out at a laser wavelength of 234 nm, corresponding to the breaking of the C-Br bond. The Br photofragment is produced in both the ground Br ((2)P3/2) and the excited Br ((2)P1/2) electronic states, and both channels are studied by the slice imaging technique, revealing new features in the velocity and angular distributions with respect to previous investigations on nonoriented molecules.
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, Taiwan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, Taiwan.
authors.forename: Shiun-Jr
authors.initials: SJ
authors.lastname: Yang
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, Taiwan.|Department of Chemistry, National Chung-Hsing University , Taichung, Taiwan.
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Tsai
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, Taiwan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kasai
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, Taiwan.|Institute of Atomic and Molecular Sciences, Academia Sinica , Taipei, Taiwan.
authors.forename: King-Chuen
authors.initials: KC
authors.lastname: Lin
authors.affiliation: Graduate School of Science, Department of Chemistry, Osaka University , Osaka, Japan.
authors.forename: Dock-Chil
authors.initials: DC
authors.lastname: Che
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Perugia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lombardi
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Perugia, Italy.|Scuola Normale Superiore , Pisa, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Palazzetti
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Perugia, Italy.|Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia , 00016 Roma, Italy.|Insituto de Fìsica, Universidade Federal da Bahia , Salvador, Brazil.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Aquilanti