title: Combined theoretical and experimental study of the valence, Rydberg and ionic states of fluorobenzene.
abstract: New photoelectron spectra (PES) and ultra violet (UV) and vacuum UV (VUV) absorption spectra of fluorobenzene recorded at higher resolution than previously, have been combined with mass-resolved (2 + 1) and (3 + 1) resonance enhanced multiphoton ionization (REMPI) spectra; this has led to the identification of numerous Rydberg states. The PES have been compared with earlier mass-analyzed threshold ionization and photoinduced Rydberg ionization (PIRI) spectra to give an overall picture of the ionic state sequence. The analysis of these spectra using both equations of motion with coupled cluster singles and doubles (EOM-CCSD) configuration interaction and time dependent density functional theory (TDDFT) calculations have been combined with vibrational analysis of both the hot and cold bands of the spectra, in considerable detail. The results extend several earlier studies on the vibronic coupling leading to conical intersections between the X(2)B1 and A(2)A2 states, and a further trio (B, C, and D) of states. The conical intersection of the X and A states has been explicitly identified, and its structure and energetics evaluated. The energy sequence of the last group is only acceptable to the present study if given as B(2)B2<C(2)B1<D(2)A1, a conclusion which is in agreement with most previous EOM-CCSD and other calculations. However, this symmetry ordering of the B and C states forces reconsideration of the nature of the PIRI spectrum. The coupling between these two states is induced by the a2 modes, ν12 and ν14 and we propose that the 14(1) band is observed in the B(2)B2 band in the PES for the first time, because of the improved resolution. This same assignment is given to the lowest energy band in the PIRI spectrum which was previously assigned as the origin band and further conclude that the entire PIRI spectrum is induced by ν12 and ν14. The relative intensities of the various Rydberg state peaks in the VUV absorption and REMPI spectra of fluorobenzene are very similar to those observed in the equivalent spectra of benzene.
authors.affiliation: School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, Scotland EH9 3FJ, United Kingdom.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Palmer
authors.affiliation: School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, Scotland EH9 3FJ, United Kingdom.
authors.forename: Trevor
authors.initials: T
authors.lastname: Ridley
authors.affiliation: ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Vrønning Hoffmann
authors.affiliation: ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
authors.forename: Nykola C
authors.initials: NC
authors.lastname: Jones
authors.affiliation: CNR-ISM, Basovizza Area Science Park, 1-34149 Trieste, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Coreno
authors.affiliation: CNR-IOM Laboratorio TASC, Trieste, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: de Simone
authors.affiliation: CNR-IOM Laboratorio TASC, Trieste, Italy.
authors.forename: Cesare
authors.initials: C
authors.lastname: Grazioli
authors.affiliation: Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden.
authors.forename: Teng
authors.initials: T
authors.lastname: Zhang
authors.affiliation: International Centre for Quantum and Molecular Structures, College of Sciences, Shanghai University, 99 Shangda Road, Shanghai 200444, China.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Biczysko
authors.affiliation: Scuola Normale Superiore, Piazza Cavalieri 7, 56126 Pisa, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Baiardi
authors.affiliation: Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, USA.
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Peterson