Math & Science ⇒ mhchem | White Space with multi-line Brace in Equations

[hugovdberg]

It's been a while since I have been here, but now I have another question and maybe I'm just too picky but I don't like the spacing (both horizontally and vertically) in the following example (which is based on a stackoverflow answer on this page):

Code: Select all

\documentclass{scrartcl}
\usepackage{amsmath}
\usepackage[version=3]{mhchem}

\begin{document}
\begin{align*}
\cee{N2 + O2   &->[\text{high temperature}] 2NO}\\
\begin{array}{r}\cee{
   NO + O3\\
   NO + HO2
   }\end{array}
   &
\left.\begin{array}{l}\cee{
   -> NO2 + O2\\ 
   -> NO2 + OH
   }\end{array}\right\} \text{or} \\
\cee{NO2 + OH &-> HNO3\\
HNO3  &-> H+ + NO3-}
\end{align*}
\end{document}

I have tried combining the two {array} environments, but then the reactions don't align with the surrounding reactions at all (left aligned on the page). I have also tried to surround the lines without a brace with {array} environments, which lines them up more nicely, but I do not like the large white space to the left of the reaction arrow. And does anyone know how to make the reaction arrows all the same length?

Also there is a little more vertical white space above and below the braced lines then between the bottom two lines, but that's just a minor thing, maybe that's fine because of the brace which extends a little above and below the lines.

The PDF output of the MWE is attached.

[cgnieder]

This is probably the space around the array columns. Try setting \arraycolsep=0pt or remove the space manually be specifying the columns like @{}r@{} and @{}l@{}.

Regards

[hugovdberg]

@localghost Sorry, I overlooked the attachment option, thanks for fixing that!
However, I'm not sure if this really is a mhchem specific problem, since the original solution also has the extraneous whitespace.

@cgnieder Thanks for that solution, I ended up adding {array} environments around the right-hand part of each equation and specifying the columns like you said. It looks way nicer now, and I'll go with the little extra vertical space.

I fixed the wider arrows myself with \hphantom, now the arrows are all the same length.