Chiral-Selective Chemistry Induced by Spin-Polarized Secondary Electrons from a Magnetic Substrate R. A. Rosenberg, 1 M. Abu Haija, 1 and P.J. Ryan 2 1 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA 2 MUCAT, Ames Laboratory, Ames, Iowa 50011, USA (Received 20 May 2008; published 21 October 2008) We demonstrate for the first time that low-energy spin-polarized secondary electrons, produced by irradiation of a magnetic substrate, can induce chiral-selective chemistry. Our approach was to perform detailed 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 substrate. The results showed that there is an enhancement of 10% in the rate of CO bond cleavage that depends on the chirality of the molecule and the spin polarization of the substrate secondary electrons. DOI: 10.1103/PhysRevLett.101.178301 PACS numbers: 82.50.Nd, 82.50.Kx, 96.55.+z Because of the fundamental nature that handedness (chirality) plays in biological processes, researchers have been striving for years to discover the possible mechanisms that could have led to this property [1,2]. External agents that are thought to induce chirality in organic molecules, such as circularly polarized UV photons and longitudinal spin-polarized electrons, have been extensively investi- gated with varying degrees of success [3–12]. It is widely recognized that delivery of exterrestrial organic com- pounds to Earth by comets or interstellar dust particles may be a potential source of prebiotic (leading to life) molecules. Furthermore, chiral amino acids have been detected in meteorites [13]. Thus, a significant effort has been directed towards understanding radiation-induced re- actions occurring in the interstellar medium [5,7–9,14]. In the present Letter, we hypothesize that a previously un- considered chiral agent can play a role in chiral-selective chemistry: namely, low-energy spin-polarized secondary electrons, produced by photon [15,16], electron [17,18], or ion [19] irradiation of a magnetic substrate. The direction of the spin is determined by the relative orientation of the magnetization vector with respect to the propagation di- rection of the particle beam. To test this premise we have performed detailed 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 (Fe 0:2 Ni 0:8 ) substrate. We show that there is an enhancement of 10% in the rate of C-O bond cleavage that depends on the chirality of the molecule and the spin polarization of the substrate secondary elec- trons. This enhancement is well above that seen in most previous studies [1–12]. Furthermore, the present mecha- nism is more general in that it requires only a magnetic substrate and a source of ionizing radiation. Iron is one of the most common elements and is magnetic in many forms. Ionizing radiation and magnetic fields are ubiquitous throughout the Universe. Therefore, this proposed mecha- nism for inducing chirality should be viable in a wide variety of possible environments. Our approach involves monitoring C-O bond cleavage of a model chiral molecule, (R) or (S)-2-butanol (CH 3 CHOHC 2 H 5 , see models in Fig. 1), adsorbed on a magnetic Permalloy (Fe 0:2 Ni 0:8 ) substrate, as a function of x-ray irradiation time. The chiral carbon on 2-butanol is bound to an -OH group. Experiments were carried out under UHV conditions using x-ray photoelectron spectros- FIG. 1 (color online). C 1 s XPS spectrum of (R )-2-butanol adsorbed on Permalloy at 90 K obtained at the start of a photolysis series. The points are the raw data; the dashed lines are the individual fitted components, and the solid line is the synthesized curve. The filled-in region represents the C-O peak, which directly probes the chiral carbon. Also shown are models of (S)- and (R)-2-butanol. PRL 101, 178301 (2008) PHYSICAL REVIEW LETTERS week ending 24 OCTOBER 2008 0031-9007= 08=101(17)=178301(4) 178301-1 Ó 2008 The American Physical Society