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Physical Sciences: Level Populations of Excited States of Hydrogen in Gaseous Nebulae

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Abstract

THE radiation from hydrogen atoms which is observed at radio and millimetre wavelengths due to atomic transitions between levels of high quantum number n cannot be accounted for without accurate calculations of the population densities of all the levels1,2. In order to interpret the observed intensities3, and to deduce physical parameters such as temperatures and abundances, accurate calculations of level populations are needed. In gaseous nebulae the physical processes which may populate and depopulate a quantum level are radiative capture and cascade, collisional ionization and three-body recombination, collisional transitions (n→n′) induced by electrons and protons, and radiative transitions induced by the free–free continuum within the nebula. Calculations have been made over a large range of temperatures and densities and for all n. The results should be much more accurate than any available previously.

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Authors and Affiliations

  1. Department of Physics, University College London,

    M. BROCKLEHURST

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  1. M. BROCKLEHURST
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BROCKLEHURST, M. Physical Sciences: Level Populations of Excited States of Hydrogen in Gaseous Nebulae. Nature 225, 618–619 (1970). https://doi.org/10.1038/225618a0

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  • DOI: https://doi.org/10.1038/225618a0

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