Principle and basic design of omnidirectional photoelectron acceptance lens

Abstract

We propose a ±90°-acceptance spherical aberration-corrected electrostatic lens based on the cathode lens technique used in photoemission electron microscopy. This lens, which we call “omnidirectional photoelectron acceptance lens (OPAL)”, is aimed at realizing 2π-steradian photoelectron spectroscopy in a wide energy range. For this lens, modifications of a simple cathode lens were studied in detail by ray-tracing calculations. Then, modified cathode lenses were combined with a decelerating mesh lens in order to achieve a focusing lens with a full acceptance angle of ±90°. Some basic designs of the lens are presented. These designs allow for 2π-steradian photoelectron spectroscopy not only in the UPS regime, but also in the XPS regime, which may open new horizons in photoelectron spectroscopy.

Photoelectron Momentum Microscope at BL6U of UVSOR-III synchrotron

“…Recently, several new designs have been developed using an ellipsoidal mesh lens to achieve better energy resolution [35][36][37] and a wider acceptance angle of 2π steradians at kinetic energy up to 1 keV. 38) By combining a focused soft-X-ray beam together with a sample position scanning mechanism, scanning microscopic photoelectron spectroscopy and diffraction measurements from small and/or polycrystalline samples were realized. 39) HDAs are widely used to measure energy and angular dependence of photoelectron intensity (binding energy E b versus wave number k) for angle-resolved photoelectron spectroscopy (ARPES).…”

“…In order to collect photoelectrons beyond the k-FoV limit, it is necessary to reshape the extractor to make the opening larger. 38) With a photon energy range up to 800 eV covered by the BL6U, core-level excitation of a variety of important elements is possible. Resonant momentum-resolved photoelectron spectroscopy is a promising method that opens the door to elemental-and orbital-selective valence band dispersion mapping.…”

Use of planar retarding field to improve energy resolution of projection-type electron spectroscopy collimator analyzer

“…High energy resolution XPD measurements with wide angular acceptance were realized by combining a wide acceptance angle electrostatic lens (WAAEL) with a concentric hemispherical analyzer (CHA), [10][11][12] allowing HXPD measurements of electron kinetic energy up to around 10 keV. 10,11) In addition, various designs and applications of WAAEL [13][14][15][16][17][18][19][20][21] are possible. Display-type ellipsoidal mesh analyzer (DELMA) 18) is a combination of WAAEL and a lens system.…”

Contrast Inversion of Photoelectron Spectro-microscopy Image

“…This requires a longer acquisition time and causes a shift in the measurement position on the sample surface. Consequently, input lenses with deflectors [2−4] and spherical aberration correction mesh lenses [5,6] were later developed to measure the angular distribution of photoelectrons from a fixed irradiation spot on the sample surface.…”