Unravelling overlaps and torsion-facilitated coupling using two-dimensional laser-induced fluorescence

Kemp, David J.; Gardner, Adrian M.; Tuttle, William D.; Wright, Timothy G.

Abstract

Two-dimensional laser-induced fluorescence (2D-LIF) spectroscopy is employed to identify contributions to fluorescence excitation spectra that arise from both overlapping bands and coupling between zero-order states (ZOSs). Evidence is found for the role of torsional motion in facilitating the coupling between vibrations that particularly involves the lowest-wavenumber out-of-plane vibrational modes. The experiments are carried out on jet-cooled p-fluorotoluene, where the molecules are initially in the lowest two torsional levels. Here we concentrate on the 390–420 cm−1 features in the S1 ← S0 excitation spectrum, assigning the features seen in the 2D-LIF spectrum, aided by separate dispersed fluorescence spectra. The 2D-LIF spectra allow the overlapping contributions to be cleanly separated, including some that arise from vibrational-torsional coupling. Various coupling routes open up because of the different symmetries of the lowest two torsional modes; these combine with the vibrational symmetry to provide new symmetry-allowed vibration-torsion (‘vibtor’) interactions, and the role of the excited m = 1 torsional level is found to be significant.

Citation

Kemp, D. J., Gardner, A. M., Tuttle, W. D., & Wright, T. G. (2019). Unravelling overlaps and torsion-facilitated coupling using two-dimensional laser-induced fluorescence. Molecular Physics, 117(21), 3011-3026. https://doi.org/10.1080/00268976.2018.1554865

• Journal Article Type: Article
• Acceptance Date: Nov 27, 2018
• Online Publication Date: Dec 9, 2018
• Publication Date: Nov 2, 2019
• Deposit Date: Dec 10, 2018
• Publicly Available Date: Dec 10, 2019
• Journal: Molecular Physics
• Print ISSN: 0026-8976
• Electronic ISSN: 1362-3028
• Publisher: Taylor & Francis Open
• Peer Reviewed: Peer Reviewed
• Volume: 117
• Issue: 21
• Pages: 3011-3026
• DOI: https://doi.org/10.1080/00268976.2018.1554865
• Keywords: Physical and Theoretical Chemistry; Biophysics; Molecular Biology; Condensed Matter Physics
• Public URL: https://nottingham-repository.worktribe.com/output/1395124
• Publisher URL: https://www.tandfonline.com/doi/full/10.1080/00268976.2018.1554865