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

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


David J. Kemp

Adrian M. Gardner

William D. Tuttle

Timothy G. Wright


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.


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.

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
Keywords Physical and Theoretical Chemistry; Biophysics; Molecular Biology; Condensed Matter Physics
Public URL
Publisher URL


Tim Wright Unravelling Overlaps And Torsion-facilitated Coupling (1.1 Mb)

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