Electron pair emission from surfaces: Some general experimental considerations

TL;DR

This paper reviews experimental methods for studying electron pair emission from surfaces, comparing two types of spectrometers and discussing key measurement considerations for accurate results.

Contribution

It provides a comparative analysis of hemispherical analyzers and time-of-flight spectrometers for electron pair emission experiments, including measurement techniques and performance evaluation.

Findings

Different approaches to determine true and random coincidence ratios.

Primary flux must be lower than in single electron spectroscopy.

Operational strategies like delayed coincidence circuits improve measurement accuracy.

Abstract

We discuss some experimental facets of electron pair emission from surfaces using two different experimental approaches. In the first case the instrument consists of a pair of hemispherical analyzers which are operated with continuous primary beams of electrons or photons. The second instrument employs a pair of time-of-flight spectrometers which require a pulsed excitation source. A key experimental quantity is the ratio of `true' to `random' coincidences which can be determined in different ways. Regardless of the type of instrument the primary flux has to adopt a much smaller value than in single electron spectroscopy. We describe different approaches to obtain the relevant count rates, in particular the concept of operating with a delayed coincidence circuit. We also address the question on how to compare the two types of spectrometer in terms of their performance.