fBelow are a selection of plots which show linear attenuation coefficient as a function of energy in different materials. These plots come from the Harshaw catalog “Harshaw Radiation Detectors”.

Sodium Iodide - NaI ( High Resolution PDF)
Lead - Pb ( High Resolution PDF )
Aluminum - Al ( High Resolution PDF)
Iron - Fe ( High Resolution PDF)
Copper - Cu (|High Resolution PDF)