Lets say I am in free-fall towards some massive body and I have 2 mirrors and photons bouncing in between them. Now as I fall closer to the massive body the light should get blue-shifted right? And lets say that the frequency of light that I started with is x. As I fall closer I put a jar of neon atoms in between the mirrors. And lets say that is takes x+d frequency to excite these neon atoms. By now the light has been shifted to x+d. But in my frame wouldn't I still see frequency x. Or does the energy levels of the atom change as we fall down?