On the classical theory of molecular optical activity

TL;DR

This paper reviews classical and semi-classical theories of molecular optical activity, introducing a tensor framework and linking optical rotation with circular dichroism through fundamental relations, while discussing potential measurements in the vacuum ultraviolet region.

Contribution

It introduces a tensor-based approach to molecular optical activity and clarifies the relation between optical rotation and circular dichroism using fundamental principles.

Findings

All phenomena can be described with one pseudo-scalar function of frequency.

Optical rotation and circular dichroism are related via Kramers-Kronig relations.

Nine molecular tensors are sufficient to evaluate optical activity at any frequency.

Abstract

The basic principles of classical and semi-classical theories of molecular optical activity are discussed. These theories are valid for dilute solutions of optically active organic molecules. It is shown that all phenomena known in the classical theory of molecular optical activity can be described with the use of one pseudo-scalar which is a uniform function of the incident light frequency $\omega$. The relation between optical rotation and circular dichroism is derived from the basic Kramers-Kronig relations. In our discussion of the general theory of molecular optical activity we introduce the tensor of molecular optical activity. It is shown that to evaluate the optical rotation and circular dichroism at arbitrary frequencies one needs to know only nine (3 + 6) molecular tensors. The quantum (or semi-classical) theory of molecular optical activity is also briefly discussed. We also raise the possibility of measuring the optical rotation and circular dichroism at wavelengths which correspond to the vacuum ultraviolet region, i.e. for $\lambda \le 150$ $nm$.