Über die galaktischen Nebel und den Ursprung der Nebellinien

N II Electric Quadrupole Transition Rate Measured at a Heavy-Ion Storage Ring

“…(This is the very transition discussed in the report below.) In his 1935 report on "the spectrum and composition of the gaseous nebulae" [9] (see also [10]) Bowen lists a wavelength prediction of 5755.0 Å for the N II 2s 2 2p 2 1 D 2 -1 S 0 transition, alongside with a 1928 measurement by Becker and Grotrian [11] that yielded a wavelength of 5754.8 Å observation of the nebulae NGC 7027 and NGC 6572. Condon [12] showed that for typical nebular lines the dominant decay was by magnetic dipole (M1) radiation, the electric quadrupole (E2) contribution being several orders of magnitude weaker.…”