rearranging week 1

src/1_einstein_model.md

@@ -155,8 +155,6 @@ ax.set_ylabel('$C/k_B$')
 ax.set_ylim((0, 3));
 ```
 
-[^1]: The data in this plot is the same as what Einstein used, but the curve in this plot is improved compared to what Einstein did, see [this blog post](https://quantumtinkerer.tudelft.nl/blog/footsteps-of-einstein/) for the backstory.
-
 ## Exercises
 
 ### Exercise 1: Heat capacity of a classical oscillator.
@@ -205,3 +203,5 @@ Naturally occurring lithium has [two stable isotopes](https://en.wikipedia.org/w
 2. Write down the total energy of lithium assuming that all $^6$Li atoms are in $n=2$ vibrational state, and all $^7$Li atoms are in $n=4$ vibrational state.
 3. Write down the total energy of lithium at a temperature $T$ by modifying the Einstein model.
 4. Compute the heat capacity of lithium as a function of $T$.
+
+[^1]: The data in this plot is the same as what Einstein used, but the curve in this plot is improved compared to what Einstein did, see [this blog post](https://quantumtinkerer.tudelft.nl/blog/footsteps-of-einstein/) for the backstory.