thomson-scattering.tex

\documentclass[tikz,border=5pt]{standalone}

\usepackage{amsmath}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{fadings,shadings}

\tikzfading[name=fade out,
    inner color=transparent!0,
    outer color=transparent!100]

\pgfdeclareradialshading{atomshade}{
    \pgfpoint{0cm}{0cm}}
    {
        color(0cm)=(pgftransparent!0);
        color(0.2cm)=(pgftransparent!20);
        color(0.5cm)=(pgftransparent!50);
        color(0.7cm)=(pgftransparent!70);
        color(1cm)=(pgftransparent!100)
    }

\tikzset{atom/.style={circle, shading=atomshade, minimum size=1.0cm}}

\begin{document}
\begin{tikzpicture}
	% Settings for incoming wave
	\def\incomingWaveStart{-1.833}
	\def\incomingWaveEnd{-1.2165}
	\def\incomingArrowStart{-1.2165}
	\def\incomingArrowEnd{-1.0996}

	% Settings for scattered waves
	\def\scatteredWaveStart{0}
	\def\scatteredWaveEnd{0.633}
	\def\scatteredArrowStart{0.633}
	\def\scatteredArrowEnd{0.75}
	\def\oscillationAmplitude{0.1}
	\def\frequencyFactor{2.0e3}

	% General settings
	\def\atomRadius{0.55} % Radius of atom
	\def\waveLengthLabelPosX{-1.7}
	\def\waveLengthLabelPosY{0.0}
	\def\highlightAngle{135}
	\def\opacityHigh{1}
	\def\opacityLow{0.65}

	% Atom
	\node[atom=gray] (atom1) at (0,0) {};

	% Oscillations
	\foreach \radius in {0.85, 0.95, 1.05, 1.15} {
			\draw[path fading=fade out, thick] (\radius cm - 0.20cm, 0.05cm) arc (15:75:\radius cm);
			\draw[path fading=fade out, thick] (-\radius cm + 0.20cm, -0.05cm) arc (195:255:\radius cm);
		}

	% Incoming x-ray wave
	\draw[black, variable=\x, samples=200, smooth, domain=\incomingWaveStart:\incomingWaveEnd]
	plot( \x, {-\oscillationAmplitude + \oscillationAmplitude * cos(\frequencyFactor*\x)} );
	% Arrow segment at the end
	\draw[->, black, variable=\x, samples=20, smooth, domain=\incomingArrowStart:\incomingArrowEnd]
	plot( \x, -\oscillationAmplitude);
	\node [above] at (\waveLengthLabelPosX,\waveLengthLabelPosY) {$\lambda$};

	% Emitted x-rays
	\foreach \angle in {95, \highlightAngle, 165, 275, 315, 350} {
			\pgfmathsetmacro{\startX}{\atomRadius * cos(\angle)}
			\pgfmathsetmacro{\startY}{\atomRadius * sin(\angle)}
			\pgfmathparse{\angle==\highlightAngle ? \opacityHigh : \opacityLow}
			\let\op\pgfmathresult

			% Wave packet
			\draw[black, opacity=\op, variable=\x, samples=200, smooth, domain=\scatteredWaveStart:\scatteredWaveEnd]
			plot({
					\startX + \x * cos(\angle) - \oscillationAmplitude * sin(\frequencyFactor*\x)*sin(\angle)
				}, {
					\startY + \x * sin(\angle) + \oscillationAmplitude * sin(\frequencyFactor*\x) * cos(\angle)
				});

			% Arrow at the end
			\draw[->, black, opacity=\op, variable=\x, samples=20, smooth, domain=\scatteredArrowStart:\scatteredArrowEnd]
			plot({
					\startX + \x * cos(\angle)
				}, {
					\startY + \x * sin(\angle)
				});
		}
	\node [left, opacity=\opacityLow] at (+95:1.1) {$\lambda$};
\end{tikzpicture}
\end{document}