title: Combined theoretical and experimental study of the valence, Rydberg, and ionic states of chlorobenzene.
abstract: New photoelectron (PE) and ultra violet (UV) and vacuum UV (VUV) spectra have been obtained for chlorobenzene by synchrotron study with higher sensitivity and resolution than previous work and are subjected to detailed analysis. In addition, we report on the mass-resolved (2 + 1) resonance enhanced multiphoton ionization (REMPI) spectra of a jet-cooled sample. Both the VUV and REMPI spectra have enabled identification of a considerable number of Rydberg states for the first time. The use of ab initio calculations, which include both multi-reference multi-root doubles and singles configuration interaction (MRD-CI) and time dependent density functional theoretical (TDDFT) methods, has led to major advances in interpretation of the vibrational structure of the ionic and electronically excited states. Franck-Condon (FC) analyses of the PE spectra, including both hot and cold bands, indicate much more complex envelopes than previously thought. The sequence of ionic states can be best interpreted by our multi-configuration self-consistent field computations and also by comparison of the calculated vibrational structure of the B and C ionic states with experiment; these conclusions suggest that the leading sequence is the same as that of iodobenzene and bromobenzene, namely: X(2)B1(3b1 (-1)) < A(2)A2(1a2 (-1)) < B(2)B2(6b2 (-1)) < C(2)B1(2b1 (-1)). The absorption onset near 4.6 eV has been investigated using MRD-CI and TDDFT calculations; the principal component of this band is (1)B2 and an interpretation based on the superposition of FC and Herzberg-Teller contributions has been performed. The other low-lying absorption band near 5.8 eV is dominated by a (1)A1 state, but an underlying weak (1)B1 state (πσ(∗)) is also found. The strongest band in the VUV spectrum near 6.7 eV is poorly resolved and is analyzed in terms of two ππ(∗) states of (1)A1 (higher oscillator strength) and (1)B2 (lower oscillator strength) symmetries, respectively. The calculated vertical excitation energies of these two states are critically dependent upon the presence of Rydberg functions in the basis set, since both manifolds are strongly perturbed by the Rydberg states in this energy range. A number of equilibrium structures of the ionic and singlet excited states show that the molecular structure is less subject to variation than corresponding studies for iodobenzene and bromobenzene.
authors.affiliation: School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, Scotland.
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 EH9 3FJ, Scotland.
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