A set of either two → electric dipoles or two → magnetic dipoles in close proximity to each other arranged with alternating polarities and acting as a single unit. Quadrupole interactions are much smaller than dipole interactions, but can allow transitions forbidden in dipole moment transitions.
Fr.: anisotropie quadrupolaire
The → anisotropy which is at the origin of the → cosmic microwave background polarization. The quadrupole anisotropy could arise from three types of perturbations: → scalar perturbation, → vector perturbation, and → tensor perturbation
Fr.: lentille quadrupôle
Fr.: moment quadrupolaire
A quantity characterizing an electric charge distribution, determined by the product of the charge density, the second power of the distance from the origin, and a spherical harmonic over the charge distribution.