Polycapillary-boosted instrument performance in the extreme ultraviolet regime for inverse photoemission spectroscopy.

Christoph Braig,Xeniya Kozina,Regan G Wilks,Sempfira Bjeoumikhova,Thomas Kunze,Marcus Bär,Markus Thiel,Andrey Sokolov,Alexei Erko

doi:10.1364/oe.25.031840

Abstract

A collimating polycapillary half lens, traditionally used in the medium and hard X-ray band, is operated at a photon energy of 36 eV for the first time. While the transmission still exceeds 50%, the measured and simulated spatial resolution and angular divergence approach 0.4 mm or less and at most 20 mrad, respectively. This unexpected, superior performance of the polycapillary optic in the extreme Ultraviolet could enable the design of an efficient, versatile and compact spectrometer for inverse photoemission spectroscopy (IPES): Its wavelength-dispersive component, a customized reflection zone plate, can maintain an energy resolution of 0.3 eV, whereas the sensitivity may be enhanced by more than one order of magnitude, compared to conventional spectrometers. Furthermore, the overall length of 0.9 m would allow for an eased alignment and evacuation. We see a significant potential for numerous polycapillary-based XUV / soft X-ray instruments in the future, in particular after further optimization for this long wavelength regime.

Highlights

Inverse photoemission spectroscopy (IPES) provides access to the unoccupied density of states
In the XUV- and x-ray range, reflection zone plates (RZPs) as “all-in-one” dispersive and focusing optics may help to realize these properties with minimized complexity [3]
The paper is organized as follows: In Sect. 2, we present experiments which characterize the polycapillary half lens (PCL) at an energy of 36 eV

Summary

Introduction

Inverse photoemission spectroscopy (IPES) provides access to the unoccupied density of states. Depending on the injection of electrons of fixed or variable energy, the emitted photons may be either recorded over an extended range in the spectrometric or – at a specified wavelength – in the isochromatic mode [1, 2]. 2, we present experiments which characterize the PCL at an energy of 36 eV. Based on these empirical findings for the PCL behavior, we sketch in Sect. 4 a possible instrumental design for a potential, future IPES spectrometer at 36 eV and study an extension of its range of use to a wide energy range in Sect. 6 discusses both the specific experimental results for the PCL and the induced, but so far only calculated performance of the planned spectrometer

Objectives

Methods

Findings

Conclusion