Abstract
The forbidden O I lines at , 6300, and 6363 appear as faint absorption lines in the solar spectrum. Measurements of the equivalent widths indicate that the reversing layer has 7× oxygen atoms per square centimeter. Comparison with the equivalent widths of the infra-red permitted lines yields an excitation temperature of 5200° for oxygen. The possibility of using forbidden lines for determining the abundance of other light elements is discussed.
DOI:https://doi.org/10.1103/RevModPhys.20.109
©1948 American Physical Society