Abstract
The absolute photoabsorption cross sections of norbornadiene (NBD) and quadricyclane (QC), two isomers with chemical formula C7H8 that are attracting much interest for solar energy storage applications, have been measured from threshold up to 10.8 eV using the Fourier transform spectrometer at the SOLEIL synchrotron radiation facility. The absorption spectrum of NBD exhibits some sharp structure associated with transitions into Rydberg states, superimposed on several broad bands attributable to valence excitations. Sharp structure, although less pronounced, also appears in the absorption spectrum of QC. Assignments have been proposed for some of the absorption bands using calculated vertical transition energies and oscillator strengths for the electronically excited states of NBD and QC. Natural transition orbitals indicate that some of the electronically excited states in NBD have a mixed Rydberg/valence character, whereas the first ten excited singlet states in QC are all predominantly Rydberg in the vertical region. In NBD, a comparison between the vibrational structure observed in the experimental 11B1–11A1 (3sa1 ← 5b1) band and that predicted by Franck–Condon and Herzberg–Teller modeling has necessitated a revision of the band origin and of the vibrational assignments proposed previously. Similar comparisons have encouraged a revision of the adiabatic first ionization energy of NBD. Simulations of the vibrational structure due to excitation from the 5b2 orbital in QC into 3p and 3d Rydberg states have allowed tentative assignments to be proposed for the complex structure observed in the absorption bands between ∼5.4 and 7.0 eV.
| Original language | English |
|---|---|
| Article number | 064305 |
| Journal | Journal of Chemical Physics |
| Volume | 160 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 14 Feb 2024 |
Bibliographical note
Funding Information:The work was performed on the DESIRS beamline at the SOLEIL synchrotron radiation facility under Proposal No. 20210065. The authors are grateful to the scientific and technical staff of SOLEIL for the efficient operation of the storage ring and beamline. The authors thank Marcello Coreno (ELETTRA) for providing data files containing the photoelectron spectra of NBD and QC (measured at the GasPhase beamline) discussed in the work of Palmer et al. (Ref. ) and Dr. Achim Zahl (Friedrich–Alexander University Erlangen–Nürnberg) for measuring the NMR spectrum. D.M.P.H. thanks the Science and Technology Facilities Council (United Kingdom) for financial support. J.C.C. acknowledges a doctoral studentship from the University of Oxford. A.K. acknowledges funding from the Engineering and Physical Sciences Research Council (Nos. EP/V049240/2, EP/V006819/2, EP/X026698/1, and EP/X026973/1) and the Leverhulme Trust (No. RPG-2020-208). S.B., M.C., K.C., A.R., A.K., P.M.W., and D.R. acknowledge funding by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-SC0020276. K.B., H.V.S.L., and E.W. were supported by Award No. DE-FG02-86ER13491 from the same funding agency. A.O. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-SC0017995. A.R.A. and A.S.V. were funded through the National Science Foundation (NSF) Grant No. PHYS-1753324. J.B. and M.B. acknowledge funding by the German Science Foundation (DFG), Grant No. 392607742.
Funding Information:
The work was performed on the DESIRS beamline at the SOLEIL synchrotron radiation facility under Proposal No. 20210065. The authors are grateful to the scientific and technical staff of SOLEIL for the efficient operation of the storage ring and beamline. The authors thank Marcello Coreno (ELETTRA) for providing data files containing the photoelectron spectra of NBD and QC (measured at the GasPhase beamline) discussed in the work of Palmer et al. (Ref. 24) and Dr. Achim Zahl (Friedrich-Alexander University Erlangen-Nürnberg) for measuring the NMR spectrum. D.M.P.H. thanks the Science and Technology Facilities Council (United Kingdom) for financial support. J.C.C. acknowledges a doctoral studentship from the University of Oxford. A.K. acknowledges funding from the Engineering and Physical Sciences Research Council (Nos. EP/V049240/2, EP/V006819/2, EP/X026698/1, and EP/X026973/1) and the Leverhulme Trust (No. RPG-2020-208). S.B., M.C., K.C., A.R., A.K., P.M.W., and D.R. acknowledge funding by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-SC0020276. K.B., H.V.S.L., and E.W. were supported by Award No. DE-FG02-86ER13491 from the same funding agency. A.O. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-SC0017995. A.R.A. and A.S.V. were funded through the National Science Foundation (NSF) Grant No. PHYS-1753324. J.B. and M.B. acknowledge funding by the German Science Foundation (DFG), Grant No. 392607742.
Publisher Copyright:
© 2024 Author(s).