We can
(%i1) texput(me,"\\mu_e");
(%o1) \mu_e
(%i2) tex(me);
$$\mu_e$$
(%o2) false
"$$\mu_e$$" is the right answer.
But why not? (See the following)
(%i3) tex("\\mu_e");
$$\mu\_e$$
(%o3) false
Notice the difference of $$\mu\_e$$ and $$\mu_e$$.
YC