90°-deflection imaging electron analyzer for measuring wide 2D angular distribution and perpendicular spin texture

Abstract

A 90°-deflection imaging electron analyzer for measuring wide 2D angular distribution and perpendicular spin texture is proposed. This analyzer, which we call “right-angle-deflection imaging analyzer (RADIAN)”, provides electrostatic 90°-deflection and 2D focusing of an electron beam. Here a large acceptance angle comparable to that of cylindrical mirror analyzer (CMA) is achieved without using a grid, while CMA uses grids at the entrance and the exit of an electrostatic field. The 90° deflection allows measuring spin polarization not only in the in-plane direction, but also in the surface-normal direction. Basic properties of RADIAN, calculated by ray tracing, are shown in comparison with those of the most widely used electron energy analyzer, i.e., concentric hemispherical analyzer (CHA). RADIAN has a much higher 2D focusing capability than CHA and allows a much larger acceptance angle for 2D imaging. Moreover, the high focusing capability of RADIAN allows us to obtain high energy resolution comparable to that obtained in CHA. A simple and effective way to achieve higher energy resolution is to combine two or more RADIANs in tandem. Double-pass and triple-pass analyzers in this combination are taken into account. For a practical application, we consider a combination of RADIAN with the recently proposed ±90° omnidirectional photoelectron acceptance lens. RADIAN can be suitably used to develop a wide-angle 2D imaging analyzer, and can also be used to develop a spin-resolved 2D imaging analyzer that can perform perpendicular-spin-texture imaging.