Visible and infra-red sensitivity of Rayleigh limit and Penndorf extension to complex refractive index of soot

THE RAYLEIGH limit of the classical Lorenz-Mie (LM) theory is widely utilized in thermal radiation when the particle diameter is small relative to the wavelength of radiation [I+]. This approximation is usually assumed to be accurate up to the size parameter CI = nD/I 2 0.3, D being the particle diameter, i; the wavelength of radiation. The extension of Rayleigh bound from GI 1 0.3 to o[ g 0.8 has been suggested by Penndorf [5] and employed by Ku and Felske [6], and Selamet and Arpaci [7, 81. Selamet and Arpaci have also assessed the upper bounds of the two approximations by examining the percent error involved in the range I.5 < n < 2.5 and 0.5 < k ,( 1.5, n and k being respectively refractive and absorptive index of particles, and applied the Penndorf expansion to soot and thermal radiation interaction. Dispersion parameters ref. [9] ref. [IO] ref. [14]