Probing molecular chirality with a femtosecond reaction microscope
Date | Mo, 13.05.2013 | |
Time | 16:45 | |
Speaker | Bhargava Ram, LaserLab, Vrije Universiteit, Amsterdam, The Netherlands | |
Location | ETH Zurich, Hönggerberg Campus, HPF G-6 | |
Program | Chirality is a ubiquitous phenomenon in the universe - found in sub atomic particles like neutrinos to large biological molecules like RNA, DNA, amino acids etc. In day to day life, chiral molecules find their usage in many products for eg. pharmaceuticals, food flavors etc. The abundant usage requires detecting chiral molecules and their handedness in a simple, sensitive and selective way. While many conventional optical techniques based on circular dichroism in absorption are used, their sensitivity is of the order of 0.01 %. Photoionization of chiral molecules in gas phase using circularly polarized light has emerged as a promising technique in identifying molecular chirality. Single photon ionization experiments using synchrotron light sources have routinely reported upto 10% asymmetry in the photoelectron angular distributions (PADs) – an improvement of 3 orders of magnitude in chiral sensitivity over conventional circular dichroism technique. In a significant development, it is possible to achieve such high sensitivities using commercially available table-top femtosecond lasers with high peak intensities (~1012 W/cm2) via multiphoton excitation and ionization of chiral molecules. Such a multiphoton excitation scheme can lead to enhancement of the PECD magnitude due to alignment in the intermediate Rydberg states. In this talk, I will describe the phenomenon of 'photoelectron circular dichroism (PECD)' and present details of the experiments performed on chiral molecules (camphor, borneol etc.) with femtosecond laser pulses and a single velocity map imaging spectrometer for detecting electrons and ions in coincidence. Host: Hans Jakob Wörner, Laboratorium für Physikalische Chemie, LPC |
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Link | Programme |