# Fix a formula with fraction 1/2 in subscript mode

At this time for my book I am writing some formulas for radioactive decay. I'm using actually newtxtext package as a text font and mt2pro as a mathematical character and formula font. In the attached code I use newtxmath so that everyone can compile it regularly keeping in mind that the situation is the same using mt2pro. Precisely I would like to write the fraction 1/2 similar to the image below (green rectangle), In other words, the backslash should be very close to the number 1 and 2, because as you can see in the formula (2), the expression is not only not visually good.

We appreciate your suggestions and your knowledge to make the visualization of my formulas better (especially the exponent of the formula (2)).

Here my MWE for 2nd image: \documentclass[12pt,a4paper]{book}
\usepackage{newtxtext,newtxmath}
\usepackage{mathtools}

\begin{document}
\begin{equation}
T_{1/2}=\frac {\ln 2}{\lambda}=\tau \ln 2<\tau
\end{equation}

\begin{equation}
N(t)=N_0e^{-\frac{t\ln 2}{T_{1/2}}}=N_0e^{\ln 2^{-\frac t{T_{1/2}}}}=N_0{2}^{-\frac{t}{T_{1/2}}}
\end{equation}

\end{document}


The digit 1 is much thinner than the other digits. Most fonts, however, define it with a bounding box equal to the ones for the other digits, for the sake of alignment in tables.

You can solve the special case by defining a suitable command:

\documentclass{article}
\usepackage{newtxtext,newtxmath}

\newcommand{\one}{\mspace{-1mu}1\mspace{-1.5mu}}

\begin{document}

\begin{equation}
T_{\one/2}=\frac {\ln 2}{\lambda}=\tau \ln 2<\tau
\end{equation}

\begin{equation}
N(t)=N_0e^{-\frac{t\ln 2}{T_{\one/2}}}=
N_0e^{\ln 2^{-\frac t{T_{\one/2}}}}=N_0{2}^{-\frac{t}{T_{\one/2}}}
\end{equation}

\end{document}


I wouldn't touch the slash. I would also omit the step with the fraction at second level superscript: it is unreadable and actually an easy application of logarithms. A short explanation after the equation is more than sufficient.

\documentclass[12pt,a4paper]{book}
\usepackage{newtxtext,newtxmath}
\usepackage{mathtools}
\usepackage{nicefrac}

\begin{document}
\begin{equation}
T_{\nicefrac{1}{2}}=\frac {\ln 2}{\lambda}=\tau \ln 2<\tau
\end{equation}

\begin{equation}
N(t)=N_0e^{-\frac{t\ln 2}{T_{\nicefrac{1}{2}}}}=N_0e^{\ln 2^{-\frac t{T_{\nicefrac{1}{2}}}}}=N_0{2}^{-\frac{t}{T_{\nicefrac{1}{2}}}}
\end{equation}

\end{document} 