Recombination lines of excited hydrogen in compact radio sources associated with galaxies and quasars

It is shown that recombination lines of excited hydrogen in absorption may be detected in compact radio sources identified with galaxies and quasars, and having a high-frequency (not less than 5 GHz) point of contrary flexure in the spectrum. It is shown that these lines may be detected if the turnover is due to free-free absorption of the radiation of the compact source by ionized hydrogen located near the source. Results are presented on expected excited-hydrogen lines for the compact sources 3C84 and P2134+00 for purely thermal motion with an electron temperature of 10,000 K and for turbulent velocities of 200 km/s.