overruling subscripts in latex export

[Peter Rayner <prayner@unimelb.edu.au>]

I'm documenting some code including lists of parameters.  These have
underscores in them which I don't want to interpret as subscripts.
According to the manual I can overrule this behaviour with an option
but it looks like I'm doing something wrong.

Here is the test file
#+OPTIONS: ^:{}
#+TITLE: test file

- p_c_in :: this is the first parameter 
- g_c_in :: and this is the second



And here is the exported latex
% Created 2012-01-25 Wed 12:04
\documentclass[11pt]{article}
% package includes deleted 

\title{test file}
\author{Peter Rayner}
\date{25 January 2012}

\begin{document}

\maketitle

\setcounter{tocdepth}{3}
\tableofcontents
\vspace*{1cm}


\begin{description}
\item[p$_c$$_{\mathrm{in}}$] this is the first parameter
\item[g$_c$$_{\mathrm{in}}$] and this is the second
\end{description}

\end{document}

Note those $ signs in the \item brackets.  I would rather see
p\_c\_in  or \verb|p_c_in|

I am probably misunderstanding how to set the option, could someone
please explain?

This is with
Org-mode version 7.5 (release_7.8.03.74.gd6e40f)
Thanks in advance
Peter



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