\begin{figure}[H]
  \begin{center}
    \unitlength=4pt
    \begin{picture}(72, 32)(4,-4)
    \gasset{Nw=5,Nh=5,Nmr=2.5,curvedepth=0}
    \thinlines
    \node[Nmarks=i,iangle=180](A1)(36,18){$1$}
    \node(A2)(54,18){$12$}
    \node[Nmarks=f,fangle=270](A3)(54,0){$13$}
    \node(A4)(0,18){$\emptyset$}
    \node(A5)(18,18){$2$}
    \node[Nmarks=f,fangle=270](A6)(18,0){$3$}
    \node[Nmarks=f,fangle=270](A7)(36,0){$23$}
    \node[Nmarks=f,fangle=270](A8)(72,0){$123$}
    \drawedge(A1,A2){$a$}
    \drawedge(A3,A1){$b$}
    \drawedge(A6,A4){$a,b$}
    \drawedge(A5,A6){$a,b$}
    \drawedge(A7,A6){$a,b$}
    \drawedge(A2,A8){$a$}
    \drawedge(A8,A3){$b$}
    \drawloop[loopangle=90](A1){$b$}
    \drawloop[loopangle=90](A4){$a,b$}
    \drawloop[loopangle=0](A8){$a$}
    \gasset{curvedepth=4}
    \drawedge(A2,A3){$b$}
    \drawedge(A3,A2){$a$}
    \end{picture}
  \end{center}
  \caption{Après déterminisation...}
\end{figure}