4755 20200203154343.0 10.1093/mnras/stz857 DOI SCART-2020-0055 Guzmán, F. 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 2019 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. NO atomic data atomic processes masers H II regions radio lines: general submillimetre: general Astrophysics - Astrophysics of Galaxies Physics - Atomic Physics Chatzikos, M. van Hoof, P. A. M. Balser, Dana S. Dehghanian, M. Badnell, N. R. Ferland, G. J. Monthly Notices of the Royal Astronomical Society 486 2019 1 1003-1018 peter.vanhoof@observatoire.be https://arxiv.org/abs/1903.05730 published in REFERD