Represent an arc over letters

I want to have a flat arc over some letters. How is it possible?

\documentclass{article}
\usepackage{graphicx,amsmath}
\newcommand\bigfrown[2][\textstyle]{\ensuremath{%
\array[b]{c}\text{\scalebox{2.4}{$#1\frown$}}\\[-1.3ex]#1#2\endarray}}

\begin{document}

\bigfrown{PQR}

\end{document}

-

Instead of scalebox you may use resizebox

\documentclass{article}
\usepackage{graphicx,amsmath}
\newcommand\bigfrown[2][\textstyle]{\ensuremath{%
\array[b]{c}\text{\resizebox{6ex}{.7ex}{$#1\frown$}}\\[-1.3ex]#1#2\endarray}}

\begin{document}

\bigfrown{PQR}

\end{document}


This is very manual and you have to adjust the parameters of resizebox by yourself.

Edit:

Atleast with this code you don't have to guess the width:

\documentclass{article}
\usepackage{graphicx,amsmath,calc}
\newlength{\mywidth}
\newcommand\bigfrown[2][\textstyle]{\ensuremath{%
\array[b]{c}\text{\resizebox{\mywidth}{.7ex}{$#1\frown$}}\\[-1.3ex]#1#2\endarray}}

\begin{document}
\settowidth{\mywidth}{PQRSPQ}
\bigfrown{PQRSPQ}

%\setlength{\mywidth}{0pt}
\settowidth{\mywidth}{PQR}
\bigfrown{PQR}

\end{document}


-
Thank you very much. –  user12290 Dec 8 '12 at 2:24
@user12290: You are welcome. Glad it helped. –  Harish Kumar Dec 8 '12 at 3:43