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MO: Molekülphysik

MO 15: Photoionisation II (gemeinsam mit FV Atomphysik)

MO 15.5: Vortrag

Donnerstag, 7. März 2002, 15:00–15:15, HS 15/E10

Circular Dichroism in the Ion Yield of Alanine — •Georg Prümper, Slobodan Cveanovic, Jens Viefhaus, Toralf Lischke, Daniel Rolles, Oliver Geßner, and Uwe Becker — Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany

Amino acids have an intrinsic chirality which is the cause of well known effects like optical activity. It has been suggested that photofragmentation of amino acids with circularly polarized light could be a possible mechanism for the creation of an racemic excess. High values for racemic excess of extraterrestrial amino acids were found in the Murchison meteorite. In order to test the hypothesis of enantioselective photodecomposition of free molecules, measurements in the gas phase are neccessary. In our experiment we measured the circular dichroism in the partial and total ion yield of L- and D-amino acid vapour. We used a time-of-flight ion mass spectrometer with pulsed electric fields for the ion extraction and identification of the masses. In the same measurements we were permanently looking for dependencies of the partial ion yield on the helicity of the light, i.e. the circular dichroism (CD) in the partial ion yield. We have determined the ionic fragmentation channels in the VUV region 10eV to 30eV and around the C(1s) edge between 280eV and 310eV.