[Tex/LaTex] Astrophysical notation : typeset HI

formattingtypography

What would the best way to typeset HI to designate molecular gas as in the title of this article, with a capital H and a slightly smaller numeral I ? I am using the scrbook class.

I tried to define

\newcommand{\HI}{H {\uppercase{\romannumeral 1}} }

but this results in H i, with a lowercase i.

I also tried

\newcommand*{\HI}{\textsc{Hi}}

but this doesn't behave properly when I use it in \section{}, resulting in "H i" rather than "H I".

I also haven't found anything like this in chemmacros, which is more geared towards chemists.

This is a standard way of writing molecules in astrophysics, so I'm surprised there isn't a package that does this easily.

Best Answer

Use the size of subscripts linked to the current font size.

\documentclass{article}
\usepackage{amsmath}

\makeatletter
\DeclareRobustCommand{\HI}{%
  \mbox{H\check@mathfonts\fontsize\sf@size\z@\selectfont I}%
}
\makeatother

\textheight=3cm % just to shorten the image

\begin{document}

\section{About \HI}

Here we talk about \HI.\footnote{Yes, about \HI.}

\end{document}

The kernel command \check@mathfonts computes \sf@size and \ssf@size starting from the current font size, either with the parameters stored with \DeclareMathSizes or with a heuristic otherwise.

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I think that in these cases is good to refer to some standards, such as those of the International Telecommunication Union: E.123 : Notation for national and international telephone numbers, e-mail addresses and web addresses. (Section 2 Notation for National and International Telephone Numbers, of the English version).

[Tex/LaTex] How are amounts of money to be typeset

It is probably overkill, but I usually use siunitx. Here is an example

\documentclass{article}
\usepackage{siunitx}

\sisetup{
  group-four-digits = true,
  group-separator = {,}
}

\begin{document}

I looked in my bank account and saw  \SI{15}[\$]{M}!
But then I woke up, and there was only \SI{457.34}[\$]{}.
I cried a little, but then I got paid and there was \SI{2456.23}[\$]{}.

\end{document}

Output produced from the above example

This shows a compact way of writing large numbers (the $15M), the typesetting of normal amounts ($457.34) and the way siunitx will sort out where to put the commas (in the $2,456.23).

Depending on the font you use, you might want to put in the $\,$ , if it looks too cramped to you. In the above example, I probably would. But it is easy to define a macro to wrap that in:

\newcommand{\usd}[1]{\SI{#1}[\$\ensuremath{\,}]{}}

UPDATE: I based on the comments, I should add that in the US, the SI standard of using a thin space to group triplets is not well followed. For me, it is certainly preferable to follow the standard, but consider your audience. If you can get away with it, use group-separator = {\,}.

Best Answer

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