| 释义 |
neˈbulium
[f. nebul-a + -ium: orig. called nebulum.]
An element distinguished by a green line it was held to produce in the spectrum of gaseous nebulæ, but not otherwise evidenced.
It is now considered that no such element exists, the lines formerly attributed to it having been identified with those produced by known elements.
1898Sir W. Crookes Addr. Brit. Assoc. 19 Still awaiting discovery by the fortunate spectroscopist are the unknown celestial elements Aurorium..and Nebulum. 1899Atlantic Monthly Apr. 469 It is an impressive fact that hydrogen and nebulium are the only elements recognized in the nebulae. 1937J. W. T. Spinks tr. Herzberg's Atomic Spectra & Atomic Struct. iv. 157 Bowen..first showed that the nebulium lines, which had been observed in the spectra of many cosmic nebulae but were long a complete mystery, were to be explained as forbidden transitions between the deep terms of O+ (4S, 2D, 2P), O++ (3P, 1D, 1S), and N+ (3P, 1D, 1S). 1940Astrophysical Jrnl. XCII. 408 The free electrons, liberated from hydrogen by photoionization, may excite the ‘nebulium’ lines by inelastic impact. 1965Phillips & Williams Inorg. Chem. I. ii. 43 Transitions between these states in atomic spectra are also ‘forbidden’, but they have been observed for the isoelectronic N+ and O2+ ions in the spectra of cosmic nebulae (so called nebulium lines). 1973L. Oster Mod. Astron. xiii. 205 For a long time, in fact until 1928, the origin of some of the strongest lines was unclear, and, in desperation, they were ascribed by some astronomers to a hypothetical element called nebulium. |