Dresden 2011 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 7: Resonance Ionization MS, REMPI, MALDI
MS 7.4: Vortrag
Mittwoch, 16. März 2011, 17:00–17:15, GÖR 229
Circular dichroism in ion yields employing femtosecond laser ionization — •Philipp Horsch1, Gunter Urbasch1, Dominik Kröner2, and Karl-Michael Weitzel1 — 1Philipps-Universität Marburg, Chemistry Department — 2Universität Potsdam, Chemistry Department
Recently, we have demonstrated the determination of circular dichroism (CD) in mass spectrometry using left- and right-circular polarized femtosecond laser pulses. [1] To adress the pivotal question, whether the CD depends on the laser pulse duration, we have investigated the CD in ion yield of 3-methyl-cyclopentanone by means of experiment and theory as a function of the laser pulse duration. [2] In the experiment the CD in ion yield is measured by femtosecond laser ionization via a one-photon resonant excited state. In the theoretical part the CD is calculated by solving laser driven quantum electron dynamics for the same resonant excitation based on ab initio electronic structure calculations. Both the experimentally measured CD in ion yields and the calculated CD in excited state populations exhibit a marked increase of the CD for pulse duration increasing from 50 fs to about 200 fs. Beyond 200 fs pulse duration the CD levels off. The combination of experimental and theoretical evidence indicates that the CD decreases with increasing laser intensity connected to the increased coupling between the excited state manifold. [1] H. G. Breunig, G. Urbasch, P. Horsch, J. Cordes, U. Koert, K. M. Weitzel, ChemPhysChem, 2009, 10, 1199-1202. [2] P. Horsch, G. Urbasch, K. M. Weitzel, D. Kröner, Phys. Chem. Chem. Phys., 2010, in press