# Ionization Energy and Electron Affinity

This is from my textbook. But in other reference books I am using and Wikipedia, there is not any mention of absolute zero while defining Ionization Energy and Electron Affinity. What does it mean? Please Elaborate

• At temperatures higher than zero, electrons may gain energy from thermal excitations. en.m.wikipedia.org/wiki/Electron_excitation Because of these thermal excitations the highest occupied state may change. However, I am not sure if temperature is that important. I would think that the temperature that a material has to reach to for electrons to go above the Fermi energy would have to be quite high – CoffeeIsLife Apr 6 '16 at 1:05
• I think the definition of the ionization energy is related to the ground state configuration, that is implied at the zero temperature. – freude Apr 6 '16 at 4:39

Also, if this was not done the $\Delta H$ values would in effect have double counted the effect of temperature, once in the ionisation energy and again in the heat capacity term.