Magnetic dipole and electric quadrupole interactions in the theory of first-order spatial dispersion phenomena

Abstract

The theory of the molecular optical response in the first-order spatial dispersion approximation is developed. It is shown that in the absence of a DC electric and/or magnetic field the electric quadrupole and magnetic dipole interactions are inseparable on the microscopic level. The equations for first-, second- and third-order hyperpolarizabilities, which are responsible for such polarization phenomena as natural and light-induced polarization plane rotation and quadrupole second harmonic generation are obtained.