Mössbauer spectrum

The dips have the same position (all be it less intense) for T=50K and T=18K except for the middle. This tells us the following:
1. The hyperfine field has the same strength because the levels are split exactly the same
2. At higher temperatures relaxation effects lead to reduced intensity for some transitions but averaging over for others like the middle here

The different response to increase of temperature could be explained by different transition rates. At higher temperatures the hyperfine field will oscillate faster and if this is faster than the transition rate, this could lead to averaging out.