What is the different of the emissivity(des_em) and radiation coeficient(ic_gama_rs)?

hello everyone:
I have a question about 2 parameters in the mfix-dem model: I am confused about the emissivity(des_em) in the solids-materials subpanel, and the radiation coeficient(ic_gama_rs) in the IC-solid subpanel? what the different of the two parameters?
mfix-22.1