Guzmán, F. ; Chatzikos, M. ; van Hoof, P. A. M. ; Balser, Dana S. ; Dehghanian, M. ; Badnell, N. R. ; Ferland, G. J.

published in Monthly Notices of the Royal Astronomical Society, 486 issue 1, pp. 1003-1018 (2019)

Abstract: At intermediate to high densities, electron (de-)excitation collisions are the dominant process for populating or depopulating high Rydberg states. In particular, the accurate knowledge of the energy changing (n-changing) collisional rates is determinant for predicting the radio recombination spectra of gaseous nebula. The different data sets present in the literature come either from impact parameter calculations or semi-empirical fits and the rate coefficients agree within a factor of 2. We show in this paper that these uncertainties cause errors lower than 5 per cent in the emission of radio recombination lines of most ionized plasmas of typical nebulae. However, in special circumstances where the transitions between Rydberg levels are amplified by maser effects, the errors can increase up to 20 per cent. We present simulations of the optical depth and Hnα line emission of active galactic nuclei broad-line regions and the Orion Nebula Blister to showcase our findings.

Keyword(s): atomic data ; atomic processes ; masers ; H II regions ; radio lines: general ; submillimetre: general ; Astrophysics - Astrophysics of Galaxies ; Physics - Atomic Physics
DOI: 10.1093/mnras/stz857
Links: link