This paper reports the observation of high-n lines in emission from n = 12-11, 13-12, 14-13 and 16-15 Rydberg transitions in H, Mg and Si in solar far IR spectra taken from balloon altitudes, in which the H I line intensities are found to exceed those from the heavier elements. Tentative identification is also made of the n = 8-7 hydrogen line in emission on 20 μm spectra taken from Mauna Kea. The characteristics of the hydrogen lines are compared with lower-n transitions seen in the Space Shuttle ATMOS spectra, in which Brackett, Pfund and n = 6 lines with Δn = 1, 2, 3 and 4 are seen as broad absorption features, while the n = 7-6 line shows a small emission peak within a broader absorption line and the n = 9-7, and possibly the 11-8, transitions appear as weak emission lines. These results indicate that the transformation from absorption to emission occurs at longer wavelengths for hydrogen lines than for those of heavier elements.
