Two-dimensional Fourier transform spectroscopy is a promising technique to study ultrafast molecular dynamics. Similar to transient absorption spectroscopy, a more complete picture of the dynamics requires broadband laser pulses to observe transient changes over a large enough bandwidth, exceeding the inhomogeneous width of electronic transitions, as well as the separation between the electronic or vibronic transitions of interest. Here, we present visible broadband 2D spectra of a series of dye molecules and report vibrational coherences with frequencies up to ∼1400 cm−1 that were obtained after improvements to our existing two-dimensional Fourier transform setup [Al Haddad et al., Opt. Lett. 40, 312–315 (2015)]. The experiment uses white light from a hollow core fiber, allowing us to acquire 2D spectra with a bandwidth of 200 nm, in a range between 500 and 800 nm, and with a temporal resolution of 10–15 fs. 2D spectra of nile blue, rhodamine 800, terylene diimide, and pinacyanol iodide show vibronic spectral features with at least one vibrational mode and reveal information about structural motion via coherent oscillations of the 2D signals during the population time. For the case of pinacyanol iodide, these observations are complemented by its Raman spectrum, as well as the calculated Raman activity at the ground- and excited-state geometry.
Broadband visible two-dimensional spectroscopy of molecular dyes
Now at: Dynamische Spektroskopien, Fakultät für Chemie, Technische Universität München, Lichtenbergstr. 4, D-85748 Garching b. München, Germany.
Now at: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
Note: This paper is part of the JCP Special Topic on Coherent Multidimensional Spectroscopy.
Lars Mewes, Rebecca A. Ingle, Andre Al Haddad, Majed Chergui; Broadband visible two-dimensional spectroscopy of molecular dyes. J. Chem. Phys. 21 July 2021; 155 (3): 034201. https://doi.org/10.1063/5.0053554
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