| AVS 55th International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS2-WeA |
| Session: | Electrons and Electronic Spectra at Surfaces |
| Presenter: | R.A. Rosenberg, Argonne National Laboratory |
| Authors: | R.A. Rosenberg, Argonne National Laboratory M.J. Abu Haija, Argonne National Laboratory P.J. Ryan, MUCAT, Ames Laboratory |
| Correspondent: | Click to Email |
Since nearly all biological compounds are homochiral, any model of the origin of life must be able to incorporate a mechanism that could lead to preferential chirality. Since chiral molecules have a certain handedness, many researchers have investigated the possible influence of circularly polarized UV photons and longitudinal spin-polarized electrons in creating an enantiomeric excess.2-4 However, in general the demonstrated effects have been small and/or on the order of the experimental error. In the present work we hypothesize that a previously unappreciated source may play a role in chiral-selective chemistry: low-energy (0-20 eV) spin-polarized secondary electrons, produced by photon,5 electron,6 or ion7 irradiation of a magnetic substrate. To test this theory we have performed detailed x-ray photoelectron spectroscopy measurements of the reaction rate for x-ray induced, secondary electron photolysis of a model chiral compound, R- or S-2-Butanol, adsorbed on a magnetized permalloy (Fe0.2Ni0.8) substrate. Our results show an enhancement of ~10% in the rate of C-O bond cleavage that depends on the chiraltiy of the molecule and the spin polarization of the secondary electrons. Not only do our results demonstrate a chirality enhancement well above that of most previous work, but, since this mechanism only requires a magnetic substrate and ionizing radiation, it should be viable in a wide variety of possible prebiotic environments.
1This work was performed at the Advanced Photon Source and was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.
2M. Avalos et al., Chem. Rev. 98, 2391 (1998).
3W. A. Bonner, Orig. Life Evol. Biosph. 25, 175 (1995).
4P. Ehrenfreund et al., Rep. Prog. Phys., 1427 (2002).
5E. Kisker, W. Gudat, and K. Schroder, Solid State Comm. 44, 591 (1982).
6J. Unguris et al., Phys. Rev. Lett. 49, 72 (1982).
7R. Pfandzelter et al., Phys. Rev. B 68, 165415 (2003).