Magnetic Dipole Absorption of Radiation in Small Conducting Particles

Abstract

We give a theoretical treatment of magnetic dipole absorption of electromagnetic radiation in small conducting particles, at photon energies which are large compared to the single particle level spacing, and small compared to the plasma frequency. We discuss both diffusive and ballistic electron dynamics for particles of arbitrary shape. The conductivity becomes non-local when the frequency is smaller than the frequency ω_c characterising the transit of electrons from one side of the particle to the other, but in the diffusive case ω_c plays no role in determining the absorption coefficient. In the ballistic case, the absorption coefficient is proportional to ω^2 for ω<< ω_c, but is a decreasing function of ωfor ω>> ω_c.