Resonances and poles of weakly absorbing spheres

Abstract

We found that the resonance positions for a weakly absorbing sphere are much different from those of a nonabsorbing sphere. The shifts of resonance positions for Qext, Qsca, and Qabs from their original resonance positions for a real refractive index are different, and the formulas to describe these different kinds of shift are given. Calculations of 12 resonance cases show that our results are quite close to those given by exact Lorenz–Mie theory. We also derive the line shapes of the different resonances and calculate values for the resonance maxima and half-width as a function of absorption.