Is there a way to reduce the space between adjacent aligns in an align environment?

Question

I want to create a series of equations on top of each other that have the same alignment. To do this I used three &'s at different points to align the symbols with each other. However, the space between the two sections it too wide, and isn't easy to read. Is there any way to fix this?

\begin{align*}
    & _{6}^{12}{C}+_{1}^{1}{H}  & \to & _{7}^{13}{N}+\gamma \\
    & _{13}^{7}{N}              & \to & _{6}^{13}{C}+e^++v_e\\
    & _{6}^{13}{C}+_{1}^{1}{H}  & \to & _{7}^{14}{N}+\gamma \\
    & _{7}^{14}{N}+_{1}^{1}{H}  & \to & _{8}^{18}{O}+\gamma \\
    & _{8}^{15}{O}              & \to & _{7}^{15}{N}+e^++v_e \\
    & _{7}^{15}{N}+_{1}^{1}{H}  & \to & _{6}^{12}{C}+_{2}^{4}{He}
\end{align*}

I do not want the arrows to be so far away, I want them to be next to the H's while still having spaces when there are less characters in the row

Answer 1

You can use tabularray to align, it can be use in math. And you should use \prescript for left subscript.

\documentclass{article}
\usepackage{tabularray}
\usepackage{mathtools}
\begin{document}
\begin{equation*}
\begin{tblr}{columns={colsep=2pt}}
\prescript{6}{12}{C}+\prescript{1}{1}{H} & \to & \prescript{7}{13}{N}+\gamma               \\
\prescript{13}{7}{N}                     & \to & \prescript{6}{13}{C}+e^++v_e              \\
\prescript{6}{13}{C}+\prescript{1}{1}{H} & \to & \prescript{7}{14}{N}+\gamma               \\
\prescript{7}{14}{N}+\prescript{1}{1}{H} & \to & \prescript{8}{18}{O}+\gamma               \\
\prescript{8}{15}{O}                     & \to & \prescript{7}{15}{N}+e^++v_e              \\
\prescript{7}{15}{N}+\prescript{1}{1}{H} & \to & \prescript{6}{12}{C}+\prescript{2}{4}{He} \\
\end{tblr}
\end{equation*}
\begin{equation*}
\begin{tblr}{cells={halign=c,valign=m},columns={colsep=1.5pt}}
\prescript{6}{12}{C} & + & \prescript{1}{1}{H} & \to & \prescript{7}{13}{N} & + & \gamma               &   &     \\
\prescript{13}{7}{N} &   &                     & \to & \prescript{6}{13}{C} & + & e^+                  & + & v_e \\
\prescript{6}{13}{C} & + & \prescript{1}{1}{H} & \to & \prescript{7}{14}{N} & + & \gamma               &   &     \\
\prescript{7}{14}{N} & + & \prescript{1}{1}{H} & \to & \prescript{8}{18}{O} & + & \gamma               &   &     \\
\prescript{8}{15}{O} &   &                     & \to & \prescript{7}{15}{N} & + & e^+                  & + & v_e \\
\prescript{7}{15}{N} & + & \prescript{1}{1}{H} & \to & \prescript{6}{12}{C} & + & \prescript{2}{4}{He} &   &     \\
\end{tblr}
\end{equation*}
\end{document}

Answer 2

ams alignments alternate between left and right aligned columns. You only want left so use && to leave the right aligned columns empty. You then need {} so the arrow gets mathbin spacing. align* adds space between each pair of columns, so use alignat which does not.

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{alignat*}{4}
    & _{6}^{12}{C}+_{1}^{1}{H} && \to {}&& _{7}^{13}{N}+\gamma \\
    & _{13}^{7}{N}           && \to {}&& _{6}^{13}{C}+e^++v_e\\
    & _{6}^{13}{C}+_{1}^{1}{H}  && \to {}&& _{7}^{14}{N}+\gamma \\
    & _{7}^{14}{N}+_{1}^{1}{H}  && \to {}&& _{8}^{18}{O}+\gamma \\
    & _{8}^{15}{O}            && \to {}&& _{7}^{15}{N}+e^++v_e \\
    & _{7}^{15}{N}+_{1}^{1}{H}  && \to {}&& _{6}^{12}{C}+_{2}^{4}{He}
\end{alignat*}
\end{document}

Answer 3

You might consider chemformula.

\documentclass{article}
\usepackage{amsmath}
\usepackage{chemformula}


\pgfkeys{
 cf /.tip = {Computer Modern Rightarrow} ,
}

\begin{document}

\begin{alignat*}{2}
\ch{
  & _{6}^{12}C + ^{1}_{1}H  && -> _{7}^{13}N + $\gamma$ \\
  & _{7}^{13}N              && -> _{6}^{13}C + e+ + $v_e$ \\
  & _{6}^{13}C + _{1}^{1}H  && -> _{7}^{14}N + $\gamma$ \\
  & _{7}^{14}N + _{1}^{1}H  && -> _{8}^{18}O + $\gamma$ \\
  & _{8}^{15}O              && -> _{7}^{15}N + e+ + $v_e$ \\
  & _{7}^{15}N + _{1}^{1}H  && -> _{6}^{12}C + _{2}^{4}He
}
\end{alignat*}

\end{document}