Berlin 2014 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Posters 1: Electronic Spectroscopy, Photochemistry, Femtosecond Spectroscopy

MO 5.17: Poster

Monday, March 17, 2014, 16:30–18:30, Spree-Palais

Phase-modulated Pump-Probe Experiments with Alkali Atoms — •Lukas Bruder, Sabrina Lipps, Mario Henne, Marcel Mudrich, and Frank Stienkemeier — Physikalisches Institut, Universität Freiburg, Germany

In view of implementing a 2D spectroscopy setup at a molecular beam apparatus, we are investigating a phase-modulation technique established by Marcus et al. [1]. In this collinear arrangement of four fs laser pulses, acousto-optical phase modulation imparts an intensity modulation on the detected nonlinear fluorescence signal. Demodulated rephasing and non-rephasing signals can be extracted using a lock-in amplifier. This method effectively decouples the relative temporal phases from the pulse envelopes and provides a high S/N scheme.

Having implemented this method in a fs pump-probe geometry with a simple gas cell, we could confirm an excellent S/N quality, a wide tuneability and great spectral resolution. Currently, we are testing the applicability to a molecular beam apparatus in a pump-probe scheme. By performing measurements with atomic alkali beams we focus on the signal detection by photo ionization and the possible combination with VMI detection. An extension to doped helium nanodroplet experiments should yield more insight in alkali-droplet coupling mechanisms.

[1] P. F. Tekavec, G. A. Lott, and A. H. Marcus, J. Chem. Phys. 127, 214307 (2007)