Title: direct spectrum
Long Title: IUPAC Gold Book - direct spectrum
DOI: 10.1351/goldbook.09320
Status: current

Definition
Spectrum of intensity of electrons transmitted and detected by a spectrometer with a dispersing energy analyser as a function of energy, \(E\).

Notes
1) In retarding field energy analysers, which do not have a dispersing element, the direct spectrum can be obtained from the first differential of the collected current with respect to the retarding energy.
2) By convention, direct spectra in X-ray photoelectron spectroscopy are often presented in constant analyser energy mode, in which the spectrum approximates the true spectrum, whereas, in Auger electron spectroscopy, spectra are often presented in constant retardation ratio mode, in which the spectrum approximates to \(E\) times the true spectrum.

Related Term
- Auger electron spectroscopy: https://goldbook.iupac.org//terms/view/09172

Source
- PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1823 (https://doi.org/10.1515/pac-2019-0404)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/09320/html
- json: https://goldbook.iupac.org/terms/view/09320/json
- xml: https://goldbook.iupac.org/terms/view/09320/xml

Citation: Citation: 'direct spectrum' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.09320
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Accessed: 2026-04-20T11:14:37+00:00