Pickering series

Pickering series

[′pik·riŋ ‚sir·ēz]
(spectroscopy)
A series of spectral lines of singly ionized helium, observed in very hot O-type stars, associated with transitions between the level with principal quantum number n = 4 and higher energy levels.
References in periodicals archive ?
The Pickering Series 120 is a range of single-pole reed relays that require a board area of 4 mm x 4 mm.
Years later lab experiments would show that the lines of the so-called Pickering series are due to absorption from singly ionized helium.
Cannon recognized in its spectrum both the Pickering series, which identified it as an O star, as well as the strong Orion lines normally associated with B stars.