The road to Ly-alpha: A historical perspective on vacuum spectroscopy

2013 marked the 100th anniversary of the publication of Niels Bohr’s atomic model which for the first time successfully explained empirically known features of hydrogen line spectra. The results of spectroscopic research on hydrogen of the late 19th and early 20th century have been key elements for the foundation of modern atomic theory. A precondition for the determination spectroscopic series beyond the visible optical domain has been the development of novel experimental and instrumental expertise on the properties of ultraviolet and infrared radiation.

This talk reconstructs the pre-history of the discovery of the first line series of hydrogen (n₁ = 1 in Rydberg’s formula), which today bears the name of its discoverer Theodore Lyman. A particular focus will be given to the experimental contributions of a self-trained and mostly self-funded individual, the amateur physicist Victor Schumann, whose work is mostly unknown today. The case of Schumann sheds light on the question to what extent outsiders to the academic world were able to contribute to the progress of physics in the second half of the 19th century.