In my simulation,I set a surface for photocathode which use the Al material.In the same time I set the QE curve of the pmt as “EFFICIENCY” of the property,during the range of QE energies,the REALRINDEX is 1.92 and the IMAGINARYRINDEX is 1.62.I wanna know how to calculate the absorption rate of this surface.(Which parameter will affect the absorption of this surface?)