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dc.contributor.authorPalmer, Michael H
dc.contributor.authorVrønning Hoffmann, Søren
dc.contributor.authorJones, Nykola C
dc.contributor.authorCoreno, Marcello
dc.contributor.authorde Simone, Monica
dc.contributor.authorGrazioli, Cesare
dc.contributor.authorAitken, R Alan
dc.identifier.citationPalmer , M H , Vrønning Hoffmann , S , Jones , N C , Coreno , M , de Simone , M , Grazioli , C & Aitken , R A 2020 , ' The vacuum ultraviolet spectrum of cyclohepta-1, 3, 5-triene : analysis of the singlet and triplet excited states by ab initio and density functional methods ' , The Journal of Chemical Physics , vol. 153 , no. 4 , 054301 .
dc.identifier.otherPURE: 269185250
dc.identifier.otherPURE UUID: eb7a01b6-4166-486b-bf0c-b14bb94ff68a
dc.identifier.otherORCID: /0000-0001-6959-5311/work/78527909
dc.identifier.otherScopus: 85089261789
dc.identifier.otherWOS: 000559816100001
dc.description.abstractThe vacuum ultraviolet (VUV) spectrum for cyclohepta-1,3,5-triene up to 10.8 eV shows several broad bands, which are compared with electron impact spectra. Local curve fitting exposed groups of sharp vibrational peaks, which are assigned to Rydberg states. The vertical excitation profile of the VUV spectrum, reproduced by time dependent density functional theory (TDDFT), gives a good interpretation of the principal regions of absorption. Fourth order Möller–Plessett perturbation theory, including single, double, and quadruple excitations, showed that the lowest singlet and triplet states retain CS symmetry. This contrasts with TDDFT where several low-lying excited states are planar. Detailed vibrational analysis of the first UV band was performed by Franck–Condon, Herzberg–Teller, and their combined methods. These show the dominance of mid-range frequencies, while the lowest frequency (75 cm−1) has negligible importance. In contrast, the second excited (Rydberg) state shows a major progression with separations of 115 (6) cm−1. This is interpreted by re-analysis of the X2A′ ionic state at the anharmonic level. Extremely low exponent Gaussian functions enabled several low-lying Rydberg state energies to be determined theoretically; extrapolation of the 3s-, 4s-, and 5s-Rydberg state calculated energies gives the adiabatic ionization energy as 7.837 eV (4) with δ 0.964 (2). Similarly, extrapolation of the centroids of the observed Rydberg states gave the vertical ionization energy (VIE) as VIE1 = 8.675 ± 0.077, close to the photoelectron spectroscopy VIE value [8.55 (1) eV].
dc.relation.ispartofThe Journal of Chemical Physicsen
dc.rightsCopyright © 2020 The Author(s). This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at
dc.subjectQD Chemistryen
dc.titleThe vacuum ultraviolet spectrum of cyclohepta-1, 3, 5-triene : analysis of the singlet and triplet excited states by ab initio and density functional methodsen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews. School of Chemistryen
dc.contributor.institutionUniversity of St Andrews. EaSTCHEMen
dc.description.statusPeer revieweden

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