A study of autoionisation in metal vapours by ejected-electron spectroscopy
A study of autoionisation in metal vapours by ejected-electron spectroscopy
A crossed-beam electron spectrometer has been used to investigate autoionisation phenomena in Li, Mg, Ca, Sr and Be vapours. High-resolution ejected-electron spectra were obtained at 75° to the direction of an incident electron beam, the energy of which could be varied between 15 eV and 500 eV. Over 400 transitions are reported; many of these have not been previously observed. It is generally found that at high electron impact energies (>200 eV) the electric dipole-allowed transitions dominate and the ejected-electron spectra in such cases closely resemble the photoabsorption spectra. At low incident electron energies, however, electric dipole-forbidden transitions become prominent. Threshold measurements have been need to determine the origin of the observed lines. The ejected-electron spectra have been analysed and many transitions are assigned by comparison with available experimental and theoretical data. In the case of Li and Mg, quantum-defect calculations have also been used to order the observed lines into series. Nearly all the lines in the ejected-electron spectra of Li and Mg have thus been identified; those in the Mg spectrum are due to the simultaneous excitation of the two valence electrons. In the heavy alkaline-earth atoms Ca, Sr and Be the cross-section for inner-shell electron ionisation (leading to the Auger effect) is found to be approximately an order of magnitude larger than the cross-section for inner-shell electron excitation (leading to autoionisation). This together with the increasing prominence with atomic number of spin-orbit interaction, prevent as thorough an analysis of these spectra as that achieved for the lighter Li and Mg atoms. Nevertheless, considerable progress has been made in unravelling these complex spectra.
University of Southampton
1981
Rassi, Dareyoush
(1981)
A study of autoionisation in metal vapours by ejected-electron spectroscopy.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A crossed-beam electron spectrometer has been used to investigate autoionisation phenomena in Li, Mg, Ca, Sr and Be vapours. High-resolution ejected-electron spectra were obtained at 75° to the direction of an incident electron beam, the energy of which could be varied between 15 eV and 500 eV. Over 400 transitions are reported; many of these have not been previously observed. It is generally found that at high electron impact energies (>200 eV) the electric dipole-allowed transitions dominate and the ejected-electron spectra in such cases closely resemble the photoabsorption spectra. At low incident electron energies, however, electric dipole-forbidden transitions become prominent. Threshold measurements have been need to determine the origin of the observed lines. The ejected-electron spectra have been analysed and many transitions are assigned by comparison with available experimental and theoretical data. In the case of Li and Mg, quantum-defect calculations have also been used to order the observed lines into series. Nearly all the lines in the ejected-electron spectra of Li and Mg have thus been identified; those in the Mg spectrum are due to the simultaneous excitation of the two valence electrons. In the heavy alkaline-earth atoms Ca, Sr and Be the cross-section for inner-shell electron ionisation (leading to the Auger effect) is found to be approximately an order of magnitude larger than the cross-section for inner-shell electron excitation (leading to autoionisation). This together with the increasing prominence with atomic number of spin-orbit interaction, prevent as thorough an analysis of these spectra as that achieved for the lighter Li and Mg atoms. Nevertheless, considerable progress has been made in unravelling these complex spectra.
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Published date: 1981
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Local EPrints ID: 459180
URI: http://eprints.soton.ac.uk/id/eprint/459180
PURE UUID: f6fc664f-06a7-4481-9bb6-47052e238f9c
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Date deposited: 04 Jul 2022 17:05
Last modified: 04 Jul 2022 17:05
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Author:
Dareyoush Rassi
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