I was looking for information on how the photo electrons are emitted when under X-ray radiation. In this ancient review paper here http://journals.aps.org/pr/pdf/10.1103/PhysRev.30.488 they state that the most common angles for non polarized X-ray beams (of various energies) range roughly at around 70-80 degrees with the beam. It is unclear to me, whether the photo electrons are moving towards the source of the X-ray beam or away from it ? Undergrad texts do not seem to shed light on this matter, the best one gets is pictures with emitted electrons being at a 90 degree angle to the incoming photon. Also, I assume this angle is given for a cone, i.e. it's 70-80 w.r.t. the beam, but with 2pi angle around the beam ?