Testing atomic collision theory with the twophoton continuum of astrophysical nebulae
Abstract
Accurate rates for energydegenerate lchanging collisions are needed to determine cosmological abundances and recombination. There are now several competing theories for the treatment of this process, and it is not possible to test these experimentally. We show that the H I twophoton continuum produced by astrophysical nebulae is strongly affected by lchanging collisions. We perform an analysis of the different underlying atomic processes and simulate the recombination and twophoton spectrum of a nebula containing H and He. We provide an extended set of effective recombination coefficients and updated lchanging 2s  2p transition rates using several competing theories. In principle, accurate astronomical observations could determine which theory is correct.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 June 2017
 DOI:
 10.1093/mnras/stx269
 arXiv:
 arXiv:1701.07913
 Bibcode:
 2017MNRAS.467.3944G
 Keywords:

 atomic data;
 atomic processes;
 H II regions;
 planetary nebulae: general;
 cosmic background radiation;
 cosmology: observations;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Physics  Atomic Physics
 EPrint:
 7 pages, 6 fig, 2 tables, accepted in MNRAS