Remarkable findings about the interaction of circularly polarized light with chiral molecules

Nottingham researchers working with colleagues, including a former Nottingham PhD student, at Soleil (the French national synchrotron source), have just published some remarkable findings about the interaction of circularly polarized light (CPL) with chiral molecules (Nature Communications 2013 4, 2132).

In recent years the Nottingham group has led the way in showing there exists an asymmetry, or imbalance, in the ejection of electrons in directions parallel and anti-parallel to the beam of ionizing CPL . This is recorded by projecting an image of the electrons, the pseudo-coloured example in the background here shows how this forward-backward asymmetry can be observed. Astonishingly, this difference can be as large as 40%, many orders of magnitude greater than previously known chiroptical effects.

In this latest work it is shown that exciting even a weak vibrational mode in the ion can completely reverse the forward-backward asymmetry – violating the Franck-Condon Principle that has guided molecular spectroscopy for nearly a century. Because of its sheer magnitude, this effect promises new capabilities for analysing chirality of mixtures and may even contribute to the left-right symmetry breaking explaining homochirality of life, i.e the dominance of left-handed amino acids and right handed sugars in the terrestrial biosphere.