Abstract
In 1811, Arago demonstrated that when linearly-polarized light passes through a chiral medium, its plane of polarization is rotated. This experimental result, called optical activity, was analyzed by Fresnel in 1825, who showed that it was complementary to a second effect, circular dichroism, in which, e.g., left-handed circularly polarized light is scattered more strongly in a chiral medium than is light with right-handed circular polarization. Optically active substances that cause clockwise rotation of the polarization plane with respect to an observer looking at the light source are called dextrorotatory, or “right-handed.” Substances that cause anti-clockwise rotations are levorotatory, or “left-handed.” These phenomena have been well-characterized in the intervening years.2 Since electrons, like photons, can be polarized,3 it is interesting to speculate that similar phenomena might be observed in electron scattering from chiral targets. Such electronic analogs would be of physical significance in their own right, but would also have interesting implications for biophysics.