# altering per-mode for a single siunitx-equation

I am using siunitx in "per-mode=symbol", and that is working very well. However now I have run into an isolated case, where I need the "per"-symbol to be ^{-1}. Here is a MWE showing what I desire:

\documentclass[10pt]{article}

\usepackage[T1]{fontenc}
\usepackage{amsmath, amsthm, amssymb}
\usepackage[ansinew]{inputenc}
\usepackage[per-mode=symbol]{siunitx}

\begin{document}
\noindent A speed of $v=\SI{888}{\meter\per\second}$, this is fine. \\
\noindent A lifetime of $\Gamma=\SI{888}{\per\second}$, not OK. It should be 888 s$^{-1}$.

\end{document}

Is there a way to define for a single "instance" that it should not use per-mode=symbol?

-
Do you mean for all \per\second cases or just this specific one given? –  Joseph Wright Oct 27 '12 at 17:36
Just this specific one. –  BillyJean Oct 27 '12 at 17:40
Perhaps $\Gamma=\SI[per-mode=reciprocal]{888}{\per\second}$? –  Paulo Cereda Oct 27 '12 at 17:40
Thanks Paulo, that worked. –  BillyJean Oct 27 '12 at 18:16
You could also write it literally as $\Gamma = \SI{888}{s^{-1}}$ (or {\second^{-1}}) but Paulo Cereda's/Joseph Wright's form is preferred. –  Qrrbrbirlbel Oct 27 '12 at 18:23

$\Gamma=\SI[per-mode=reciprocal]{888}{\per\second}$