Thanks for reply,

yes i have to take care of such things. But let me confined us within the limit, suppose the single scattering path is absorber (Cu) to Cu and multi scattering path is absorber to oxygen then back to absorber (forward scattering) and other one is absorber to oxygen then oxygen to Cu and then back to absorber, All of these have same Reff. So my question is can use the same delt_r for all of these path in which only Cu and O take place.

If all of these are different then how?

Thanks in advance