Half-Broadband Two-dimensional Electronic Spectroscopy with Active Noise Reduction

Two-dimensional electronic spectroscopy (2DES) provides detailed insight into coherent ultrafast molecular dynamics in the condensed phase. Here we report a referenced broadband pump-compressed continuum probe half-broadband 2DES spectrometer in a partially collinear geometry. To optimise signal-to-noise ratio (SNR) we implement active noise reduction referencing. The method is calibrated against the well characterised 2DES response of the oxazine dye cresyl violet and demonstrated at visible wavelengths on the photochromic photoswitch 1,2-Bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (DAE). The SNR is improved by a factor of ~2 through active referencing. We further show that active noise reduction referencing, coupled with the rapid data collection, allows the extraction of weak vibronic features, most notably a low frequency mode in the excited electronic state of DAE.