Materials Radiation properties: scattering and absorption coefficient
 

Dear all,
I am trying to moodel a solar receiver using CFX. The model is composed by both solid and fluid domains. I would like to set radiation properties for different medias but it is not clear to me what's the order of magnitude of the absorption coefficient and scattering coefficient. I am using Montecarlo ray tracing and according to guide these two coefficients represent somehow the absorption and scattering probability.
I am used with kirchoff law so I would have used a value between 1-0. Nevertheless, the frame require a value with units [m^-1]. On-line libraries give the following values in example:
Copper abs. Coeff: α = 5.9526e+5 cm-1
using these values the simulation crashes after few iterations. What am I doing wrong? what's the order of magnitude of these coefficients?
Also I would like to define an absorption coeffient with different values depending on the wavelenght in vacuum. how can I do it? I read something about step functions, can someone give me an example? Thank you ! :D