 They, however, require pulsed photon sources and are most common in laser-based ARPES labs.Electron analyzers that need a slit to prevent mixing of momentum and energy channels are only capable of taking angular maps along one direction.In order to take maps over energy and a two-dimensional momentum space, either the sample is rotated in the proper direction so that the slit receives electrons from adjacent emission angles, or the electron plume is steered inside the electrostatic lens with the sample fixed.