Fourier Transform Microwave Spectroscopy: Handedness Caught by Rotational Coherence

Optical activity can be positive or negative depending on whether the electric and magnetic dipole transition moments point into the same or opposite halves of a sphere centered on the molecule. A new technique takes a different route: Radiation emitted by molecules of opposite chirality associated with a loop of three dipole-allowed transitions between rotational states is exactly out of phase, thus providing a direct signal of molecular chirality. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.