Core Electron Transitions as a Probe for Molecular Chirality:  Natural Circular Dichroism at the Carbon K-edge of Methyloxirane

Abstract

We have measured for the first time the X-ray natural circular dichroism (XNCD) of a chiral molecule in an isotropic medium. In this condition the only surviving term contributing to CD is the cross product between the electric dipole and the magnetic dipole transition moments. The non-zero value of the magnetic dipole transition moment in a 1s-to-valence electron transition is attributed to contribution of valence states to core molecular orbitals. These results open the way to a "local" chiral molecular analysis and to the study of stereochemically selected photochemical processes.

Upper limits for the circular dichroism for the C 1s and O 1s core excitation of methyl oxirane

“…In the PIY they were found to be less than 0.5%. These upper limits do not contradict the findings of [16]. The CD in the TIY was reported to be about 0.15%.…”

“…A small CD of 0.15% in the total ion yield (TIY) of MO was found near the top of the C 1s resonance [16]. The experimental method is based on comparing the shape of the two TIY curves for the two helicities of the light.…”

Conformational Effects in Photoelectron Circular Dichroism of Alaninol

“…[2,3] The extension of NCD to the vacuum UV (VUV)-Xray range was possible with the development of the third-generation synchrotron radiation insertion devices. [4,5] From this work it appears that the order of magnitude of the dissymmetry is 10…”

Circular dichroism in photoelectron spectroscopy of free chiral molecules: Experiment and theory on methyl-oxirane

“…The first measurement of the NCD in the x-ray range exploited the full power of the third generation synchrotron radiation circularly polarized insertion devices [2], which give high brilliance and well defined polarization rates. Few works are reported in the literature concerning NCD experiments in the vuv-soft x-ray energy range [3]. First asymmetry data in vuv photoelectron angular distribution has been recently measured in evaporated bromocamphor where the dichroism was found to be of the order of few percents [4].…”