Reference equation number in subscript of equation.

Question

I have some chemical reaction equations which I want to reference in the subscript of an inline equation.

\begin{subequations}
\begin{align}
\cee{
    \text{NO} +\text{O}_3 &-> \text{NO}_2 +\text{O}_2\label{eq:example1},\\
    \text{NO} + \text{O}_3 &-> \text{NO}_2^* + \text{O}_2\label{eq:example2},

}
\end{align}
\end{subequations}


$k_{\ref{eq:example2}}$

I want to refer to eq:example 2 as the subscript for k, so if example2 was equation 1b, it would be equivalent to:

$k_{1b}$

But 1b obviously changing according to the equation numbering. Is there any way to do this, as putting \ref in the $$ symbols does not work.

Answer 1

You may just set the reference in text mode. Load amsmath or mathtools for this.

% arara: pdflatex
% arara: pdflatex

\documentclass{article}
\usepackage[version=3]{mhchem}
\usepackage{mathtools}
\usepackage{hyperref}

\begin{document}
\begin{subequations}
    \begin{align}
        \cee{NO + O3 &-> NO2 + O2\label{eq:example1}\\
            NO + O3 &-> NO2^* + O2\label{eq:example2}}
    \end{align}
\end{subequations}
 $k_\text{\ref{eq:example1}}\ne k_\text{\eqref{eq:example2}}$
\end{document}