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:
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,
};