The ionized states of 6,6-dimethylfulvene; the vibrational energy levels studied by photoionization, configuration interaction and density functional calculations

• Published in: Chemical physics letters Vol. 796; p. 139558
• Main Authors: Palmer, Michael H., Coreno, Marcello, de Simone, Monica, Grazioli, Cesare, Jones, Nykola C., Vrønning Hoffmann, Søren, Aitken, R. Alan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2022
• Subjects: Coupled cluster; Franck-Condon; Synchrotron-based Photoionization; Vibronic coupling; Vibronic coupling; Synchrotron-based Photoionization; Franck-Condon; Coupled cluster
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2022.139558

The UV-photoelectron spectrum of 6,6-dimethylfulvene recorded at hv=50 eV with the scaled symmetry-adapted cluster configuration interaction (SAC-CI) ionic states(in red).
[Display omitted]
•Synchrotron based photoionization.•Spectral assignment using symmetry-adapted cluster configuration interaction.•Franck-Condon spectral vibrational analyses.
A new synchrotron-based photoionization spectrum of 6,6-dimethylfulvene shows significant vibrational fine structure (VFS), in contrast to previous studies; this was successfully analysed by Franck-Condon (FC) methods. The sequence of ionic states in the range 7 to 19 eV has been determined by both symmetry adapted cluster configuration interaction and density functional methods, especially using the long-range corrected version of the Becke three-parameter hybrid functional (B3LYP) using the Coulomb-attenuating method (CAM-B3LYP). Both lead to reliable theoretical values for both the calculated vertical and adiabatic ionization energies. The FC profile for the lowest ionization energy (IE1, X2A2) shows extensive VFS which is analysed successfully. The second IE (A2B1) shows truncated structure owing to overlap with IE1.