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"Two dimensional Fourier transform spectroscopy in the UV with sub-20 fs pump pulses and 250 - 720 nm supercontinuum probe" N. Krebs, I. Pugliesi, J. Hauer and E. RiedleNew J. Phys. 15, 085016 (2013). Abstract: Experimental realizations of two-dimensional electronic spectroscopy in the UV must so far contend with a limited bandwidth in both the excitation and particularly the probe frequency. The pump bandwidth is at best 1,500 cm-1 (FWHM) at a fixed wavelength of 267 nm or 400 cm-1 for tunable pulses. The use of a replica of the pump pulse as probe limits the observation of photochemical processes to the excitation region and makes the disentanglement of overlapping signal contributions difficult. We show that two-dimensional Fourier transform spectroscopy can be carried out in a shaper assisted collinear setup comprising fully tunable UV pulse pairs and supercontinuum probe spanning 250 - 720 nm. The pump pulses are broadened up to a useable spectral coverage of 2,000 cm-1 (25 nm at 316 nm) by self-phase modulation in bulk CaF2 and compressed to 18 fs. By referencing the white light probe and eliminating pump stray light contributions, high signal-to-noise ratios even for weak probe intensities are achieved. Data acquisition times as short as 4 minutes for a selected population time allow the rapid recording of 2D spectra for photolabile biological samples even with the employed 1 kHz laser system. The potential of the setup is demonstrated on two representative molecules: pyrene and 2,2-diphenyl-5,6-benzo(2H)chromene. Well resolved cross peaks are observed and the excitation energy dependence of the relaxation processes is revealed. BMO authors (in alphabetic order): Jürgen Hauer Nils Krebs Igor Pugliesi Eberhard Riedle Order Hardcopy  WWW-Version |