Evans found that the 4686 series and the Pickering series can be obtained in a helium spectrum showing no trace of the ordinary hydrogen lines ... between the different theoretical interpretations ...

Black hydrogen absorption lines are at the ... Different elements produce different line spectra. A line spectrum is like a fingerprint - it can be used to identify the element present.

each pointed at a different star. The light from each star is directed through a prism to produce a spectrum. Each of the spectra has a set of absorption lines created by the presence of hydrogen ...