An angle-resolved time-of flight spectrometer for low-energy photoelectron spectroscopy

We developed and constructed a two-dimensional position-sensitive time-of-flight spectrometer (pTOF) for the angle-resolved analysis of low-energy electrons photoemitted from a metal surface by femtosecond laser pulses. The spectrometer design combines a field-free drift tube with 22 circle acceptance angle and a microchannel plate stack with a delay-line anode for position encoding. The pTOF spectrometer allows to determine both surface in-plane electron momentum components px and py along with the kinetic energy. The pTOF concept is optimized to study the electron scattering dynamics of laterally anisotropic electronic systems such as self-assembled quasi-1D atomic nano-wires or stepped surfaces. Here, we present the working principles as well as the hard- and software implementation of the pTOF, which includes real-time analysis of multiple electron hits per laser pulse. This multihit capability is crucial for pulsed laser spectroscopy with repetition rates of ∝100 kHz. To demonstrate the performance of the spectrometer measurements on a Cu(111) single-crystalline surface were performed using UV femtosecond laser pulses of 6.20 eV photon energy