\documentclass[a4paper,12pt]{report}
\usepackage{psfrag,graphicx}
\begin{document}

\begin{figure}
\includegraphics[width=.5\textwidth,angle=-90]{gamma.eps}
\hfil
\psfrag{rh113}[Bl][Bl][1.0][90]
  {\tiny $^{113}_{45}$Rh}
\psfrag{ru113}[Bl][Bl][1.0][90]
  {\tiny $^{113}_{44}$Ru}
\psfrag{ener}[t][]{$\gamma$-Energie [keV]}
\psfrag{cnt}[t][]{counts}
\psfragscanon
\includegraphics[width=.5\textwidth,angle=-90]{gamma.eps}
\end{figure}

\end{document}