Maxwell fields and Poynting vector in the proximity of a chiral molecule

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Abstract
The electromagnetic field operators for a chiral (optically active) molecule are calculated in the Heisenberg picture, using the multipolar Hamiltonian. Interactions involving electric-dipole, magnetic-dipole, and electric-quadrupole moments are taken into account. The operators are expanded in powers of moments, and expressions correct to quadratic powers in the moments are given. Comparable contributions from diamagnetic interactions are also presented. The properties of these operators are discussed. Terms that are linear in the moments are found to act in the electron space alone; those quadratic in the moments act in both the electron and photon spaces. The operators are used to calculate the Poynting vector, from which the spontaneous emission rates for magnetic-dipole and electric-quadrupole transitions are obtained. Attention is drawn to the inverse square dependence of the Poynting vector on the distance of the field point from the source. This behavior is shown to be consistent with the requirement of local conservation of energy. The operators are used in the following paper [J. K. Jenkins, A. Salam, and T. Thirunamachandran, Phys. Rev. A 50, 4767 (1994)] to calculate dispersion energies between two optically active molecules.