An Experimental and Theoretical Investigation of the 3sp(d) Rydberg States of Fenchone by Polarized laser Resonance-Enhanced-Multiphoton-ionization and Fourier Transform VUV Absorption Spectroscopy

Singh, Dhirendra; de Oliveira, Nelson; Garcia, Gustavo; Vredenborg, Arno; Powis, Ivan

Abstract

The VUV absorption spectrum of fenchone is re‐examined using Fourier transform spectrometry, revealing new vibrational structure. Picosecond laser (2+1) resonance enhanced multiphoton ionization (REMPI) spectroscopy complements this, providing an alternative view of 3 spd Rydberg excitations. These spectra are broadly similar, with minor differences that are largely explained by referring to calculated one‐ and two‐photon electronic excitation cross‐sections. Both show good agreement with Franck‐Condon simulations of the vibrational structure. Parent ion REMPI yields are studied as a function of laser polarization and intensity, the latter providing insight into the relative two‐photon excitation and one‐photon ionization rates. The experimental circular‐linear dichroism observed in the parent ion yields varies strongly between the 3 s and 3 p Rydberg states, in good overall agreement with the calculated two‐photon excitation circular‐linear dichroism, while corroborating other evidence that the 3p z sub‐state plays no more than a very minor role in the (2+1) REMPI spectrum. Vibrationally resolved photoelectron spectra are recorded with picosecond pulse duration (2+1) REMPI at selected intermediate vibrational excitations. The 3 s intermediate state displays a very strong Δ v =0 propensity on ionization, but the 3 p intermediate evidences more complex vibronic dynamics, and we infer some 3 p‐ 3 s internal conversion prior to ionization.

Citation

Singh, D., de Oliveira, N., Garcia, G., Vredenborg, A., & Powis, I. (2020). An Experimental and Theoretical Investigation of the 3sp(d) Rydberg States of Fenchone by Polarized laser Resonance-Enhanced-Multiphoton-ionization and Fourier Transform VUV Absorption Spectroscopy. ChemPhysChem, 21(21), 2468-2483. https://doi.org/10.1002/cphc.202000365

• Journal Article Type: Article
• Acceptance Date: Sep 7, 2020
• Online Publication Date: Sep 7, 2020
• Publication Date: Nov 3, 2020
• Deposit Date: Sep 7, 2020
• Publicly Available Date: Sep 8, 2021
• Journal: ChemPhysChem
• Print ISSN: 1439-4235
• Electronic ISSN: 1439-7641
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 21
• Issue: 21
• Pages: 2468-2483
• DOI: https://doi.org/10.1002/cphc.202000365
• Public URL: https://nottingham-repository.worktribe.com/output/4888074
• Publisher URL: https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cphc.202000365