is it possible to change the depth of subscripts?

Question

I have the following formula:

$ F_{\!\bm{H}}  F_{\overline{\!\!\bm{H}\!}} $

In this case both subscripts end at different depths (but start at the same height). I'd like them to end at the same depth. Has anybody an idea?

Answer 1

You can do the following:

F_{\!\bm{H}\vphantom{\overline{\!\!\bm{H}\!}}} F_{\overline{\!\!\bm{H}\!}}

The \vphantom command makes vertical space the same height its argument. Depending on how often you need this or how predictable it is, you might be able to make a macro to add the \vphantom part automatically.

Answer 2

You might want to look at the subdepth package, which has descrption

This package is based on code (posted long ago to comp.text.tex by Donald Arseneau) to equalise the height of subscripts in maths. The default behaviour is to place subscripts slightly lower when there is a superscript as well, but this can look odd in some situations.

Answer 3

$ F_{\!\bm{H}}  F_{\,\smash[t]{\overline{\!\!\bm{H}\!}}} $

Answer 4

The following changes the subscripts globally:

% for Plain with default CM-font
\fontdimen16\tensy=2.7pt
\fontdimen17\tensy=2.7pt
% Or more generally
\fontdimen16\textfont0=2.7pt
\fontdimen17\textfont0=2.7pt
$\rm Fe_2^{+2}Cr_2^{+2}O_4^{+2}$
\bye