A single line in the emission spectrum.
So precise, so discrete, which makes no sense in classical mechanics!
Has been the leading motivation of the development of quantum mechanics, all the way from the:
- Schrodinger equation: major lines predicted, including Zeeman effect, but not finer line splits like fine structure
- Dirac equation: explains fine structure 2p spin split due to electron spin/orbit interactions, but not Lamb shift
- quantum electrodynamics: explains Lamb shift
- hyperfine structure: due to electron/nucleus spin interactions, offers a window into nuclear spin
- NIST Atomic Spectra Database | 140
- Schrodinger equation | 167, 3k, 52
- Schrodinger equation solution for the hydrogen atom | 159, 372, 4
- Zeeman effect | 308