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MO: Fachverband Molekülphysik

MO 30: Poster – Molecular Spectroscopy

MO 30.12: Poster

Thursday, March 5, 2026, 17:00–19:00, Philo 1. OG

Broadband UV/Vis sub-20 fs transient absorption spectroscopy — •Marvin Krupp and Stefan Lochbrunner — Institute of Physics, Rostock, Germany

Studies on ultrafast chemical reaction steps, such as proton transfer, call for broadband spectroscopy with a time resolution below typical vibrational periods. In this work, a noncollinear optical parametric amplifier (NOPA) pumped by a Ti:Sa laser system is optimized for sub-20 fs pulses with a particular broad spectrum thus they are suitable as probe pulses for broadband transient absorption spectroscopy. The broadband NOPA enables spectral detection ranges of 490 to 900 nm and after frequency doubling of about 300 to 420 nm. Using chirped mirrors for compression, we can decrease the signal rise time at time zero of the experiment down to less than 20 fs across most spectral components. We compare these broadband NOPA measurements with uncompressed white light probing. First measurements on 2-(2*-hydroxyphenyl)-benzothiazole (HPBT) have been performed, in which proton transfer is estimated to happen on a timescale of 30-40 fs. In agreement with previous studies [1], we confirm their observations and provide a broadband analysis of the underlying proton-transfer dynamics. [1] J. Phys. Chem. A 2003, 107, 49, 10580*10590

Keywords: transient absorption spectroscopy; noncollinear optical parametric amplifier; experimental setup; proton transfer; ultrafast molecular spectroscopy