Relation between Pressure Shift, Temperature Class, and Spectral Terms of the Iron Lines

Abstract

IT has been long recognised that the lines of the iron spectrum are displaced towards the red when the pressure about their source is increased, the magnitude of the displacement being not the same for all the lines. On account of this fact Gale and Adams (Astrophys. Journ. 35, 1912, p. 10) have classified the lines in four groups, a, b, c, and d. Group a includes all the flame lines, which have small displacements. Group b is a large one and includes all the lines of small shifts which are not included in Group a. Group c consists of lines having much larger displacements than those of Group b. Group d is made up of lines which present very large displacements. An additional Group e, including lines showing displacements to the violet side, was found later by St. John and Ware (Astrophys. Journ. 36, 1912, p. 14).