Efficiency Factors in Mie Scattering

Asymptotic approximations to the Mie efficiency factors for extinction, absorption, and radiation pressure, derived from complex-angular-momentum theory and averaged over Δβ~π (β=sizeparameter), are given and compared with the exact results. For complex refractive indices $N=n+ik$ with $1.1<~n<~2.5$ and $0<~k<~1$, the relative errors decrease from {~}(1-10)% to {~}(10^-2-10^-3)% between β=10 and β=1000, and computing time is reduced by a factor of order β, so that the Mie formulae can advantageously be replaced by the asymptotic ones in most applications.