Hi,guys. I m trying to determine activation energy of donor levels . So i have measured absorption at different temperatures of my sample (mono-crystal) And I have plotted ln(optical density) vs 1/T(K). And I want to calculate activation energy useing D=D0exp(-Ea/kT) In plot above (picture) Eactivation should be 0.043eV The problem is that I cant get the right answer. Could someone help me,and derive the mentioned formula above for Ea determination? Maybe Im doing it wrong.