Table of mass attenuation coefficients for various materials.
Broken down in terms of different interaction mechanisms.
Data taken from:
	http://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html

Each file has 5 colums:
photon energy [meV]
coherent scatter [cm^2/g]
incoherent scatter [cm^2/g]
photoelectric absorption [cm^2/g]
total (with coherent) [cm^2/g]
