Two-Photon_Photoelectron_Spectroscopy
Time-resolved two-photon photoelectron (2PPE) spectroscopy is a time-resolved spectroscopy technique which is used to study electronic structure and electronic excitations at surfaces.[1][2] The technique utilizes femtosecond to picosecond laser pulses in order to first photoexcite an electron. After a time delay, the excited electron is photoemitted into a free electron state by a second pulse. The kinetic energy and the emission angle of the photoelectron are measured in an electron energy analyzer. To facilitate investigations on the population and relaxation pathways of the excitation, this measurement is performed at different time delays.
This technique has been used for many different types of materials to study a variety of exotic electron behaviors, including image potential states at metal surfaces,[1][3] and electron dynamics at molecular interfaces.[4]