Emission Lines in the Extreme Ultraviolet Spectrum of the Sun.

A solar spectrum photographed from a rocket at 115-km altitude on February 21,1955, shows 45 emission lines extending from 1892 A to 977 A. Most of the lines have been identified. The lines of highestexcitation potential arise from 0 VI, N V, C iv, and Si iv. The Lyman-a line of hydrogen was present with an intensity of approximately 0.06 watt/cm2, and its half-width was less than 0.3 A. Lyman-P was also photographed, as was the 1640.5 A line of He ii. The continuum was followed to approximately 1550 A and shows strong continuous absorption below 2085 A. The 0 vi lines are slightly limb-brightened relative to Lyman-P; the same is true for the C iv resonance lines and the He ii line at 1640.5 A, relative to lines of C I.