Recombination of helium-like ions - I. Photoionization cross-sections and total recombination and cooling coefficients for atomic helium
Abstract
A new calculation of photoionization cross-sections is described for the ground and excited states of atomic helium up to principal quantum number n=25 and angular momentum quantum number l=5. These cross-sections are used to calculate total recombination and cooling coefficients for atomic helium for electron temperatures given by log(T)=1(0.2)4.4. A comparison of the threshold photoionization cross-sections obtained here with extrapolations of the highly accurate bound-bound oscillator strength calculations by Drake shows that the new calculations are in error by no more than 1 per cent. The accuracy of the photoionization cross-sections used by previous workers to derive recombination coefficients is also discussed.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 1998
- DOI:
- 10.1046/j.1365-8711.1998.2970041073.x
- Bibcode:
- 1998MNRAS.297.1073H
- Keywords:
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- ATOMIC DATA;
- ATOMIC PROCESSES;
- LINE: FORMATION