Stuttgart 2012 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 59: Ultrakurze Laserpulse

Q 59.4: Vortrag

Freitag, 16. März 2012, 11:15–11:30, V38.04

2D-UV Spectroscopy in the Pump-Probe Geometry: First Resolution of Cross-Peaks — •Igor Pugliesi, Nils Krebs, and Eberhard Riedle — BioMolekulare Optik, LMU München

Pulses with a spectral width large enough to cover the absorption bands and compressible to the Fourier limit are the major challenge for any realization of coherent two dimensional spectroscopy. While in the IR and VIS spectral range established techniques for the generation of ultrabroad pulses are available, in the UV the methods are still in their early stages and quite demanding. We now show that spectral broadening by self-phase modulation in bulk materials offers a simple and reliable option to generate UV pulses with a spectral width of 50 THz. 20 fs UV pulses between 295 and 370 nm are generated from a NOPA and spectrally broadened by focusing the beam into a few mm thin CaF₂ crystal. They are compressed to sub-16 fs by an acousto-optic pulse shaper. In the 2D-UV setup the broadened pulse is split into a pump and a probe beam and the acousto-optic pulse shaper is then used to compress and generate the phase locked double pulses. Building on this strategy we were able to record 2D-UV spectra of the vibrational progression of the first electronic absorption band of pyrene centered at 310 nm and we resolve vibrational wavepackets as cross-peak. This result is the doorway to the direct investigation of the energy and electron transfer dynamics in DNA.