Journal article
A combined theoretical and experimental study of the valence and Rydberg states of iodopentafluorobenzene
The Journal of chemical physics, Vol.146(17), pp.174301-174301
05/07/2017
Handle:
https://hdl.handle.net/2376/116310
PMID: 28477584
Abstract
A new ultraviolet (UV) and vacuum ultraviolet (VUV) spectrum for iodopentafluorobenzene (C6F5I) using synchrotron radiation is reported. The measurements have been combined with those from a recent high-resolution photoelectron spectroscopic study. A major theoretical study, which includes both Franck-Condon (FC) and Herzberg-Teller (HT) analyses, leads to conclusions, which are compatible with both experimental studies. Our observation that the VUV multiplet at 7.926 eV in the VUV spectrum is a Rydberg state rather than a valence state leads to a fundamental reassignment of the VUV Rydberg spectrum over previous studies and removes an anomaly where some previously assigned Rydberg states were to optically forbidden states. Adiabatic excitation energies (AEEs) were determined from equations-of-motion coupled cluster with singles and doubles excitation; these were combined with time dependent density functional theoretical methods. Frequencies from these two methods are very similar, and this enabled the evaluation of both FC and HT contributions in the lower valence states. Multi-reference multi-root configuration interaction gave a satisfactory account of the principal UV+VUV spectral profile of C6F5I, with vertical band positions and intensities. The UV spectral onset consists of two very weak transitions assigned to 11B1 (πσ*) and 11B2 (σσ*) symmetries. The lowest unoccupied molecular orbital of a σ*(a1) symmetry has a significant C–I* antibonding character. This results in considerable lengthening of the C–I bond for both these excited states. The vibrational intensity of the lowest 11B1 state is dominated by HT contributions; the 11B2 state contains both HT and FC contributions; the third band, which contains three states, two ππ*(11A1, 21B2) and one πσ*(21B1), is dominated by FC contributions in the 1A1 state. In this 1A1 state, and the spectrally dominant bands near 6.7 (1A1) and 7.3 eV (1A1 + 1B2), the C–I bond length is in the normal range, and FC components dominate.
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Details
- Title
- A combined theoretical and experimental study of the valence and Rydberg states of iodopentafluorobenzene
- Creators
- Michael H Palmer - University of EdinburghSøren Vrønning Hoffmann - Aarhus UniversityNykola C Jones - Aarhus UniversityMarcello Coreno - Trieste LD2 UnitMonica de Simone - CNR-IOM Laboratorio TASCCesare Grazioli - Trieste LD2 UnitKirk A Peterson - Washington State UniversityAlberto Baiardi - Scuola Normale SuperioreTeng Zhang - University of UppsalaMalgorzata Biczysko - Shanghai University
- Publication Details
- The Journal of chemical physics, Vol.146(17), pp.174301-174301
- Academic Unit
- Department of Chemistry
- Number of pages
- 12
- Grant note
- PON01-01078/8 / muir
- Identifiers
- 99900547825501842
- Resource Type
- Journal article