Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 21: Poster 3: Cluster, Collisions, Energy Transfer, Photochemistry, Spectroscopy in He-Droplets

MO 21.24: Poster

Donnerstag, 15. März 2012, 16:30–19:00, Poster.IV

IR-spectroscopy of glycine in helium nanodroplets — •Melanie Letzner, Sarah Grün, Gerhard Schwaab, and Martina Havenith — Ruhr University Bochum, Germany

Glycine is the smallest amino acid, and therefore it is of special interest as a model and starting point for theoretical and experimental studies. Whereas the crystalline form of glycine consists of zwitterions NH₃⁺−CH₂−COO⁻, gas phase glycine is known to exist in the nonionized form NH₂−CH₂−COOH. The interaction between glycine and water has been widely studied using a large variety of theoretical methods. Depending on the theoretical level used, a stabilisation of the zwitterionic form is predicted for complexes containing from 2 to 7 water molecules. In low-temperature Ar matrices a set of characteristic IR absorption bands for the zwitterionic form has been observed. The higher stoichiometry complexes (glycine)⋯(H₂O)_n with n larger than 3 are demonstrated to be zwitterionic H-bonded complexes. The multitude of conformations expected for these glycine-water complexes makes a combination of low temperature and high resolution spectroscopy essential. We want to use the advantages of our experiment to investigate glycine and its complexes with water in helium-nanodroplets at ultracold temperatures in the range from 3000-3800 cm⁻¹. Our measurements were carried out using a high power IR-OPO (cw: 2.7 W) as radiation source and a helium nanodroplet spectrometer. Helium-nanodroplets are formed by expansion of helium at 55 bar through a 5 µm nozzle which is kept at a temperature of 16 K. The status of the project is presented.