[Tex/LaTex] Two text lines in `flalign` environment

alignhorizontal alignment

I want to achieve what the picture shows below. Basically, I want those two very long text lines to split into two lines shown below. My major problem is that if I keep the text in one line in flalign, then the entire right-side text will shift to the left. Here is my code.

enter image description here

\documentclass[a4paper]{article}
\usepackage{mathtools}
\usepackage{nccmath}
\usepackage[margin=1in]{geometry}

\newcommand \widebox[1]{\setlength\fboxsep{6pt}\boxed {\enspace#1\enspace}}
\newcommand \dpartial[2]{\frac{\partial #1}{\partial #2}}
\newcommand \ddef[2]{\frac{d #1}{d #2}}
\newcommand \spac{\\[0.6em]}

\setlength\parindent{0pt}
\numberwithin{equation}{section}

\title{\vspace{-5em} QM Formula List}
\author{David}
\date{}

\begin{document}
\maketitle
\begin{flalign*}
   &i\hbar \dpartial{\Psi}{t} = -\frac{\hbar ^2}{2m}\dpartial{^2 \Psi}{x^2}+V\Psi &&\text{Shr\"odinger Equation}\spac
   &\widehat{p} = -i \hbar \dpartial{}{x}                                         &&\text{Momentim Operator} \spac
   &\widehat{H} = -\frac{\hbar ^2}{2m} \ddef{^2 \psi}{x^2} + V                    &&\text{Energy Operator} \spac
   &-\frac{\hbar^2}{2m}\ddef{^2 \psi}{x^2} + V \psi = E \psi                      &&\text{Time-independent Schr\"odinger Equation} \spac
\end{flalign*}
\end{document}

Best Answer

Set the item in a tabular:

enter image description here

\documentclass[a4paper]{article}
\usepackage{mathtools}
\usepackage{nccmath}
\usepackage[margin=1in]{geometry}

\newcommand \widebox[1]{\setlength\fboxsep{6pt}\boxed {\enspace#1\enspace}}
\newcommand \dpartial[2]{\frac{\partial #1}{\partial #2}}
\newcommand \ddef[2]{\frac{d #1}{d #2}}
\newcommand \spac{\\[0.6em]}

\setlength\parindent{0pt}
\numberwithin{equation}{section}

\title{\vspace{-5em} QM Formula List}
\author{David}
\date{}

\begin{document}
\maketitle
\begin{flalign*}
   &i\hbar \dpartial{\Psi}{t} = -\frac{\hbar ^2}{2m}\dpartial{^2 \Psi}{x^2}+V\Psi &&\text{Shr\"odinger Equation}\spac
   &\widehat{p} = -i \hbar \dpartial{}{x}                                         &&\text{Momentim Operator} \spac
   &\widehat{H} = -\frac{\hbar ^2}{2m} \ddef{^2 \psi}{x^2} + V                    &&\text{Energy Operator} \spac
   &-\frac{\hbar^2}{2m}\ddef{^2 \psi}{x^2} + V \psi = E \psi                      &&\begin{tabular}{@{}l@{}}Time-independent \\ Schr\"odinger Equation\end{tabular} \spac
\end{flalign*}
\end{document}
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