small mods

diff --git a/solid_state_physics/tutorial/1_06s.tex b/solid_state_physics/tutorial/1_06s.tex
index f3d6992..4e965e3 100644 (file)
--- a/solid_state_physics/tutorial/1_06s.tex
+++ b/solid_state_physics/tutorial/1_06s.tex
@@ -51,11 +51,19 @@
                =\ldots=5.97 \cdot 10^{-28} \, kg\frac{m}{s}$
        \end{itemize}
  \item Phonon momentum necessary for transition:\\
-       $p=\hbar \cdot \Delta k=\hbar \cdot 0.85 \, \frac{2\pi}{a}
+       $\Delta p=\hbar \cdot \Delta k=\hbar \cdot 0.85 \, \frac{2\pi}{a}
          =\frac{0.85 \, h}{a}=\ldots=1.04 \cdot 10^{-24} \, kg\frac{m}{s}$\\
        $\rightarrow$ Phonon momentum 3 orders of magnitude below
                      the momentum necessary for transition!
- \item 
+ \item \begin{itemize}
+        \item Photon momentum insufficient.
+              Momentum contribution of phonon (lattice vibration) required.\\
+              $\Rightarrow$ Probability of transition very small.
+       \item Recombination energy of electron-hole pairs most probably
+             released as vibrational energy of the lattice.\\
+             $\Rightarrow$ Only direct band gap semiconductors suitable for
+                           effective photon generation.
+       \end{itemize}
 \end{enumerate}
 
 \section{\ldots}