1. The problem statement, all variables and given/known data I see graphs for the total mass attenuation coefficient such as this all over the web:http://scientificsentence.net/Radiations/images/attenuation_coefficients.jpg However, I can't find data on the individual attenuation coefficients such as the photoelectric or Compton attenuation coefficients. What I need is either a general formula to find them, although I imagine that the formulas will be very complex, or just experimental data on the coefficients for different elements/mediums (e.g. soft tissue). 2. The attempt at a solution http://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/tissue.html This is the closest data I could find, but it tells me nothing about the individual attenuation coefficients. Please tell me that someone reading this knows where to find this information or what to Google because I have run out of ideas. Thank you in advance.