Electronic currents induced by optical fields and rotatory power density in chiral molecules

The electric dipole–magnetic dipole polarizability tensor κ′, introduced to interpret the optical activity of chiral molecules, has been expressed in terms of a series of density functions k′αβ, which can be integrated all over the three-dimensional space to evaluate components καβ′and traceκ′αα. A computational approach to k′αβ, based on frequency-dependent electronic current densities induced by monochromatic light shining on a probe molecule, has been developed. The dependence of k′αβ on the origin of the coordinate system has been investigated in connection with the corresponding change of καβ′. It is shown that only the tracek′αα of the density function defined via dynamic current density evaluated using the continuous translation of the origin of the coordinate system is invariant of the origin. Accordingly, this function is recommended as a tool that is quite useful for determining the molecular domains that determine optical activity to a major extent. A series of computations on the hydrogen peroxide molecule, for a number of different HO–OH dihedral angles, is shown to provide a pictorial documentation of the proposed method.