Asymptotic expansion of morphological resonance frequencies in Mie scattering

A high-order asymptotic expansion for the size parameters x(n)((l)) of electromagnetic resonances of large spherical dielectric scatterers is reported. The expansion is calculated up to order n(-8/3), where n is the mode number and is valid for small orders l. Its accuracy is studied as a function of n, l, and the refractive index. For the l = 1 mode, the relative accuracy is better than 10(-4) for n > 50.