TikZ-Feynman: Reversing direction of momentum arrow

luatextikz-feynmantikz-pgf

I am trying to draw the Feynman diagram for Compton scattering.
I have come up with the following diagram, which is perfect except the leftmost arrow faces the wrong direction (I want it to denote incoming wavelength, so it should face towards the vertex).

IMAGE:

enter image description here

Does anyone know how to change the direction of this arrow?

\usepackage[compat=1.1.0]{tikz-feynman}
\feynmandiagram [scale=1.2, horizontal=f2 to f3] {
f1 [particle=\(e^{-}\)] -- [fermion] f2 -- [fermion] f3 -- [fermion] f4 [particle=\(e^{-}\)],
f2  -- [photon, edge label'=\(\gamma\), momentum=\(\lambda\)] p1,
f3 -- [photon, edge label=\(\gamma\), momentum'=\(\lambda'\)] p2,
};

Best Answer

Reading the documentation of tikz-feymann to the page 21,

enter image description here

there is the option: reversed momentum. Here the MWE with your request.

\documentclass[a4paper,12pt]{article}
\usepackage[compat=1.1.0]{tikz-feynman}

\begin{document}
   \feynmandiagram [scale=1.2, horizontal=f2 to f3] {
f1 [particle=\(e^{-}\)] -- [fermion] f2 -- [fermion] f3 -- [fermion] f4 [particle=\(e^{-}\)],
f2  -- [photon, edge label'=\(\gamma\), reversed momentum=\(\lambda\)] p1,
f3 -- [photon, edge label=\(\gamma\), momentum'=\(\lambda'\)] p2,
};
\end{document} 

enter image description here