H-, He-like recombination spectra III. n-changing collisions in highly-excited Rydberg states and their impact on the radio, IR and optical recombination lines

Guzmán, F. and Chatzikos, M. and van Hoof, P. A. M. and Balser, Dana S. and Dehghanian, M. and Badnell, N. R. and Ferland, G.J. (2019) H-, He-like recombination spectra III. n-changing collisions in highly-excited Rydberg states and their impact on the radio, IR and optical recombination lines. Monthly Notices of the Royal Astronomical Society, 486 (1). 1003–1018. ISSN 0035-8711

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    Abstract

    At intermediate to high densities, electron (de-)excitation collisions are the dominant processfor populating or depopulating high Rydberg states. In particular, the accurate knowledgeof the energy changing (n-changing) collisional rates is determinant for predicting the radiorecombination spectra of gaseous nebula. The different datasets present in the literature comeeither from impact parameter calculations or semi-empirical fits and the rate coefficients agreewithin a factor of two. We show in this paper that these uncertainties cause errors lower than5% in the emission of radio recombination lines (RRL) of most ionized plasmas of typicalnebulae. However, in special circumstances where the transitions between Rydberg levels areamplified by maser effects, the errors can increase up to 20%. We present simulations of theoptical depth and Hnαline emission of Active Galactic Nuclei (AGN) Broad Line Regions(BLRs) and the Orion Nebula Blister to showcase our findings.