Electric Octupole-Dependent Contributions to Optical Binding Energy

• Published in: Physics (Online) Vol. 6; no. 1; pp. 376 - 393
• Main Author: Salam, A.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2024
• Subjects: Approximation; Atoms & subatomic particles; Binding energy; Circular polarization; coupling of induced moments; Dipole interactions; Dipole moments; Electric dipoles; Electromagnetic fields; Energy; Energy transfer; Lasers; octupole-dependent terms; optical binding energy; Radiation; Radiation effects; real and virtual photons; Tensors
• ISSN: 2624-8174; 2624-8174
• DOI: 10.3390/physics6010025

Contributions to the radiation-induced dispersion energy shift between two interacting particles dependent on the electric octupole moment are calculated using a physical picture in which moments induced by applied fluctuating electromagnetic fields are coupled via retarded interaction tensors. The specific potentials evaluated include those found between an electric dipole-polarisable molecule and either a mixed electric dipole–octupole- or purely octupole-polarisable molecule, and those between two mixed electric dipole–octupole-polarisable molecules. Interaction energies are obtained for molecular and pair orientationally averaged situations. Terms dependent on the octupole weight-1 moment may be viewed as higher-order corrections to the leading dipole–dipole interaction energy as also found in energy transfer and dispersion forces. A comprehensive polarisation analysis is carried out for linearly and circularly polarised laser light incident parallel and perpendicular to the inter-particle axis. Contributions to the optical binding energy arising when one of the pair is polar and characterised by either a permanent electric dipole or octupole moment are also evaluated. Neither of these energy shifts survive orientational averaging.