A novel high-current, high-resolution, low-kinetic-energy electron source for inverse photoemission spectroscopy

TL;DR

This paper introduces a new high-current, high-resolution electron source for inverse photoemission spectroscopy that surpasses previous sources in current and energy resolution, with unexpected improvements attributed to a novel velocity selection mechanism.

Contribution

The paper presents a novel electron source with significantly higher current and better energy resolution for IPES, including a new understanding of electron-electron interactions.

Findings

Electron current is an order of magnitude higher than previous sources.

Energy resolution is better than predicted by standard models.

The inverse Boersch-effect explains the unexpected improvements.

Abstract

A high-current electron source for inverse photoemission spectroscopy (IPES) is described. The source comprises a thermal cathode electron emission system, an electrostatic deflector-monochromator, and a lens system for variable kinetic energy (1.6 - 20 eV) at the target. When scaled to the energy resolution, the electron current is an order of magnitude higher than that of previously described electron sources developed in the context of electron energy loss spectroscopy. Surprisingly, the experimentally measured energy resolution turned out to be significantly better than calculated by standard programs, which include the electron-electron repulsion in the continuum approximation. The achieved currents are also significantly higher than predicted. We attribute this "inverse Boersch-effect" to a mechanism of velocity selection in the forward direction by binary electron-electron collisions.