Quasi-stationary scattering of electromagnetic pulses by spherical particles

The Lorentz-Mie theory is generalized for the case of a spherical particle irradiated by a pulse with a finite length L that is transferred by a carrier wavelength λ(0). Two cases should be physically distinguished, depending on radiation-receiver properties: quasi-stationary scattering (a receiver integrates the entire signal over time) and nonstationary scattering, when a receiver is capable of recording scattered signal changes with time. General formulas that allow one to calculate optical characteristics for both scattering cases and for an arbitrary ratio L/λ(0) are derived. Quasi-stationary-scattering peculiarities and limiting cases of small and large particles are studied in detail. The formulas are illustrated with calculations of spherical-particle optical characteristics for pulses of different lengths, for differently sized particles, and for a case in which a scattered pulse has a Gaussian form. The results obtained should be taken into account when one is studying the passage of a pulse through scattering media.