# Example: Energy level diagram

Published 2009-04-29 | Author: Mark S. Everitt

A simple level diagram with some transitions.

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% Simple level diagram, resized and in a figure environment.
% Mark S. Everitt, 2009

\documentclass[10pt]{article}

% I only need the arrows for this one.
\usepackage{tikz}
\usetikzlibrary{arrows}

% Nice captions.
\usepackage[hang,small,bf]{caption}
\setlength{\captionmargin}{25pt}

% New commands to keep things tidy.
\newcommand{\ket}[1]{$\left|#1\right\rangle$}
\newcommand{\Om}[1]{\small $\omega_{#1}$}
\newcommand{\De}[1]{$\Delta_{#1}$}
\newcommand{\Ga}[1]{$\Gamma_{#1}$}

\begin{document}

% Place the TikZ picture in a figure environment.
\begin{figure}
\centerline{
% Resize it to 5cm wide.
\resizebox{7cm}{!}{
\begin{tikzpicture}[
scale=0.5,
level/.style={thick},
virtual/.style={thick,densely dashed},
trans/.style={thick,<->,shorten >=2pt,shorten <=2pt,>=stealth},
classical/.style={thin,double,<->,shorten >=4pt,shorten <=4pt,>=stealth}
]
% Draw the energy levels.
\draw[level] (2cm,-2em) -- (0cm,-2em) node[left] {\ket{a}};
\draw[level] (2cm,11em) -- (4cm,11em) node[midway,above] {\ket{b}};
\draw[level] (4cm,-11em) -- (6cm,-11em) node[right] {\ket{c}};
% Draw the virtual levels.
\draw[virtual] (2cm,8em) -- (4cm,8em) node[midway,above] {\De{1}};
\draw[virtual] (4cm,-8em) -- (6cm,-8em) node[midway,below] {\De{2}};
\draw[virtual] (2cm,-5em) -- (0cm,-5em) node[midway,above] {\De{3}};
% Draw the transitions.
\draw[trans] (1cm,-2em) -- (2.5cm,8em) node[midway,left] {\Om{1}};
\draw[trans] (3.5cm,8em) -- (5cm,-8em) node[midway,right] {\Om{2}};
\draw[classical] (4.5cm,-8em) -- (1.5cm,-5em) node[midway,below] {\Ga{}};
\end{tikzpicture}
}
}
\caption{A level diagram with some transitions drawn in TikZ, resized,
and placed in a figure environment.}
\end{figure}

\end{document}


• #1 Mark S. Everitt, May 2, 2009 at 6:15 p.m.

This example is not particularly sophisticated TikZ. I sent it in mainly to highlight how I've used a resizebox to adjust the dimensions of the picture, and a figure environment to enclose it. In this way it behaves a lot like a normal \includegraphics... in a figure environment.

• #2 Vijay, October 11, 2012 at 2:09 a.m.

Is there a reason why the comment reads "Resize it to 5cm wide." while the code calls for "\resizebox{7cm}{!}{...}"?

Pardon my ignorance: Honestly, I'm not even sure how \resizebox{}{}{} is defined.

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