# Extending arrows with overset text

I'd like to extend an arrow to allow better readability of characters which are overset using \overset{}{}.

Right now I have

 \overset{k_1}{\rightleftharpoons}


which produces:

and this leaves the subscript awfully close the to harpoon arrow. Thus, is there anyway to just extend the character length?

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There are several packages supporting extensible arrows:

An example suitable for your formula, also demonstrating the optional argument for text under the arrows:

\documentclass{article}
\usepackage{mathtools}
\begin{document}
$\xrightleftharpoons[k_2]{\,k_1\,}$
\end{document}


Output:

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Thank you, that solves the problem exactly. I've never used mathtools before. –  EricR Nov 11 '10 at 21:18