%% 
%%  An UIT Edition example
%% 
%%  Example 06-12-15 on page 113.
%% 
%%  Copyright (C) 2010 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{153.70511pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
$\sideset{^{33}_{17}}{^{16}}{\mathop{\mathrm{Cl}}}
 \xrightarrow{n,n}%
 \sideset{^{31}_{15}}{^{16}}{\mathop{\mathrm{P}}}+
 \sideset{^4_2}{^2}{\mathop{\mathrm{He}}}$
\end{document}