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Proceedings Paper

Advanced search for the origin of life's homochirality: asymmetric photon induced processes on chiral compounds with far UV circularly polarized synchrotron radiation
Author(s): Laurent Nahon; Gustavo Garcia; Ivan Powis; Uwe Meierhenrich; André Brack
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Paper Abstract

Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-acids, a possible abiotic explanation for the selection of the L enantiomers could be the exposure to an asymmetric bias such as far UV Circularly Polarized Light (CPL), during their journey towards Earth, inducing some enantiomeric excess (e.e) that could then be amplified on Earth via suitable autocatalytic mechanisms. Synchrotron Radiation (SR), with its intense flux and broad tunability, is a unique tool which mimics such an interstellar far UV CPL. We have recently employed it to study : (1) The irradiation of solid films of the amino acid D,L-leucine, i.e. under relevant astrophysical conditions. Starting from racemic D,L-leucine irradiated with CPL SR beam at 6.8 eV (182 nm), we have been able to induce by enantioselective photolysis an e.e. of 2.6 %, as measured by chiral-sensitive CG-MS analysis, in accordance with the CD spectrum recorded on the same type of sample. (2) CPL-induced gas phase photoionization of chiral molecules. By measuring the angular distribution of photoelectrons ejected from pure enantiomers, we observed a strong anisotropy (up to 16 %) in the forward/backward direction with respect to the light propagation axis. Because of momentum conservation, such an effect is accompanied by an asymmetric recoil of the corresponding ions that could lead to a high e.e. Future prospects on the new VUV SR beamline DESIRS at SOLEIL are presented.

Paper Details

Date Published: 1 October 2007
PDF: 16 pages
Proc. SPIE 6694, Instruments, Methods, and Missions for Astrobiology X, 669403 (1 October 2007); doi: 10.1117/12.729474
Show Author Affiliations
Laurent Nahon, Synchrotron Soleil (France)
Gustavo Garcia, Synchrotron Soleil (France)
Ivan Powis, Univ. Nottingham (United Kingdom)
Uwe Meierhenrich, Univ. of Nice-Sophia Antipolis (France)
André Brack, Ctr. de Biophysique Moléculaire, CNRS (France)

Published in SPIE Proceedings Vol. 6694:
Instruments, Methods, and Missions for Astrobiology X
Richard B. Hoover; Gilbert V. Levin; Alexei Y. Rozanov; Paul C. W. Davies, Editor(s)

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