Case equation without curly brace
You may better use aligned
:
\documentclass[11pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\begin{document}
\begin{equation}
\begin{aligned}
\frac{I}{Z} &= 12+\frac{7}{Z}\;[eV], && Z<13 \\
\frac{I}{Z} &= 9.76+58.8Z^{-1.19}\;[eV], && Z\geq13
\end{aligned}
\end{equation}
\end{document}
Then use a regular array
:
\documentclass{article}
\begin{document}
\begin{equation}
\renewcommand{\arraystretch}{1.3}
\begin{array}{ll}
\frac{I}{Z}=12+\frac{7}{Z}[eV], & Z<13 \\
\frac{I}{Z}=9.76+58.8Z^{-1.19}[eV], & Z\geq13
\end{array}
\end{equation}
\end{document}
The alignment specification of {ll}
inserts the contents l
eft-aligned in both columns, while a redefinition of \arraystretch
adds some vertical padding to each row. See Column padding in tables.
Since each element inside an array
is set in \textstyle
, fractions are smaller than usual by default. Adding \displaystyle
will increase the fraction presentation, similar to amsmath
's \dfrac
.