CARBON (6)
There is no evidence of the presence of neutral carbon in stellar atmospheres. The apparent absence of the element is partly due to the fact that the ultimate[160] line is at 2478, too far in the ultra-violet to be detected. The spectrum of neutral carbon is as yet unclassified, and other lines cannot, therefore, be sought for in the stellar spectrum. The temperature at which the element vaporizes is given by Kohn and Guckel[161] as 4000°, and by Violle[162] as 3800°. The heat of vaporization has been evaluated by de Forcrand.[163] At stellar temperatures, the carbon present is probably vaporized, but possibly it is largely in combination as cyanogen or as an oxide, since spectra associated with these compounds appear in low-temperature stars.
IONIZED CARBON
Ionized carbon[164] is represented in the stellar spectrum by the fundamental doublet (
), at 4267, and by the principal doublet (
) at 6580. The occurrence of these lines is of great interest. The line at 4267 is found in the
stars,[165] reaches a maximum at