Abstract
Many physical and chemical processes that shape our everyday ex-periences unfold at the atomic level in terms of both spatial dimensionsand temporal durations. Introducing temporal resolution, or the pump-probe scheme, to photoemission spectroscopy techniques serves thescientific purpose of capturing the transient electronic dynamics andinteractions on picosecond (ps, 10−12 s), femtoseconds (fs, 10−15 s) oreven attoseconds (as, 10−18 s) timescales with both time, momentumand energy resolution. This methodology enables the observation of thedevelopment of the electronic band structure and its occupancy overtime, offering valuable insights into the non-equilibrium characteristicsof quantum materials. Through the application of ultrafast laserpulses in a pump-probe setup, scientists are able to perturb the samplebeyond equilibrium with the pump pulse and subsequently examine thephotoemission response from the temporary system using the probepulse, facilitating the investigation of phenomena such as bandgapmodification, dynamics of charge carriers, and localization of wave-functions.