Most complex carbon molecules – such as those necessary for life – actually exist in two forms. The normal one and its mirror image. The left-handed version and the right-handed version.

Despite containing the same atoms, these two molecules usually have vastly different properties. For example, one might be used as a therapeutic drug, while the other could be inactive or even harmful.

Separating them is therefore very important for several reasons, particularly in the fields of chemistry, biology, and medicine. However, due to the lack of differences in the physical properties of the two molecules, this is usually quite difficult.

When any molecule is exposed to light, its quantum energy levels are split apart because of the interaction.

In this paper, the team found that when this light is circularly polarised, the splitting is different for the two mirrored molecules. They also went on to find that this effect led to different photochemical reactions for each molecule, further providing ways to distinguish them.

These effects could then be used as new methods for separating these mirrored molecules in medicine and beyond.