What is "hydrogen spectral series"

n. (context physics English) several series of spectral lines of hydrogen that correspond to quantum transitions between the various allowed energy levels of the hydrogen atom

The emission spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two energy levels in the atom. The classification of the series by the Rydberg formula was important in the development of quantum mechanics. The spectral series are important in astronomical spectroscopy for detecting the presence of hydrogen and calculating red shifts.