Physical Processes in Gaseous Nebulae. XV.
Abstract
The statistical equilibrium of an assembly of neutral helium atoms has been investigated with refer- ence to the problem of gaseous nebulae. The helium atom was assumed to contain an infinite number of energy levels, but a single equation of equilibrium was written down for all triplet levels above 2 3po and, similarly, for all singlets above 2 ipo Mean values are thus obtained for the popiilations of the high singlets and the high triplets. The population is given in terms of a quantity b~, the ratio between the true population and the value for thermodynamic equilibrium at a temperature T~. The temperature T~ refers to an assumed Maxweffian distribution of the free electrons. The nebular atoms are assumed to be opaque to the stellar radiation field oniy in the frequencies cor- responding to absorptions from levels i IS, 2 Is, and 2 ~S. Numerical solutions of the equations are tabu- lated for stellar temperatures, T1, of 50,000° and 100,000° and electron temperatures of 5000° 10,000°, 20,0000, 40,000°, and 80,0000, and also for the special case T1 = T6 = 20,0000
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1941
- DOI:
- 10.1086/144261
- Bibcode:
- 1941ApJ....93..244G