A high pressure photoemission system is described that combines differential pumping with an electrostatic lens system. This approach allows optimized differential pumping without loss of signal, thereby increasing the high-pressure performance by at least 2 orders of magnitude compared to passive differential pumping systems. A general analysis of aperture-based high-pressure photoemission is presented, followed by a description of the prototype system which has operated at pressures up to 7 mbar on a synchrotron beamline. Using this approach, photoemission experiments should be possible up to 100 mbar. Example data are presented for dielectric samples in gas atmospheres, for a copper catalyst under reaction conditions, and for liquid water in equilibrium with its vapor.
We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.
One of the key components of a time of flight (TOF) spectrometer is the detection system. In addition to high timing resolution, accurate 2-dimensional imaging substantially broadens the areas of applications of TOF spectrometers; for example, add a new dimension to angle-resolved photoemission spectroscopy (ARpES).In this paper we report on the recent developments of a high spatial (<50 pm) and timing (<130 ps) resolution imaging system capable of selective detection of electrons, ions and/or photons. Relative to our previously reported results, we have substantially improved the counting rate capabilities of the system especially for cases where the energy range of interest represents a small fraction of the incoming flux at the detector " Corresponding author.
Over the last decade, high-resolution angle-resolved photoemission spectroscopy (ARPES) has emerged as a tool of choice for studying the electronic structure of solids, in particular, strongly correlated complex materials such as cuprate superconductors. In this paper we present the design of a novel time-of-flight based electron analyzer with capability of 2D in momentum space (kx and ky) and all energies (calculated from time of flight) in the third dimension. This analyzer will utilize an improved version of a 2D delay line detector capable of imaging with <35 microns (700 x 700 pixels) spatial resolution and better than 120ps FWHM timing resolution. Electron optics concepts and optimization procedure are considered for achieving an energy resolution less than 1meV and an angular resolution better than 0.1 deg. *Corresponding author: Gennadi Lebedev, ALS, LBNL, One Cyclotron Rd.,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.