411 REFERENCE · Wiktionary
Pickering series
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
English
Etymology
Named after Edward Charles Pickering.
Proper noun
Three lines of singly ionized helium found, usually in absorption, in the spectra of hot stars, produced by transitions of an electron with principal quantum number n=4 state from a higher energy level.
en eponyms