[pstricks] Rotate and center a figure

[Denis Verges]

Hello,
My problem :

\vspace{12cm} 

\psset{xunit=6.4cm,yunit=5.5cm}
\begin{pspicture}(0,0)(3,1.5)

\rput{90}{    \psline[linewidth=1.5pt]{->}(0,0)(3,0)
   \psline[linewidth=1.5pt]{->}(0,0)(0,1.5)
   \psline[linewidth=1.5pt](0,1)(3,1)
   \uput[d](2.9,0){$x$}
   \uput[l](0,1.4){$y$}
   \uput[l](0,1){$1$}
   \uput[u](0.4,1){$\Delta$}
   \uput[dl](0,0){O}
   \uput[d](1,0){$1$}
   \psplot{0}{3}{1  x 2 exp 2.71828 1 x 2 exp sub exp mul sub}
   \uput[d](2.8,0.96){$\mathcal{C}$}}
   \end{pspicture}

... but the figure is on the left of the sheet. How center the figure ?
Thanks.
Denis Vergès