Arc spectrum of gold

Abstract

Wave-lengths of the alkali-like doublet spectrum of gold, Au I, were identified by Thorsen in 1923. The validity of Thorsen’s analysis depended on the correctness of his choice of the resonance lines, 6 s 2 S—6 p 2 P 0 . The classification of these was confirmed and what was believed to be (but see below) the second member of the 2 S— 2 P 0 series identified by the authors who, two years later, observed absorption of the two pairs of wave-lengths by normal vapour of gold. A metastable term of inverted 2 D type and a higher one with 2 P 0 characteristics that did not belong to the simple doublet spectrum were evaluated by us also. In a subsequent investigation of Au I, the authors found that the value of one component of the metastable 2 D term was not real and succeeded in re-evaluating the level correctly. A number of higher terms in addition to the irregular 2 P 0 was observed also. These and the metastable 2 D term were shown to be a part of the complex spectrum built on the 5 d 6 s ion and predicted by the Hund theory that had been just then introduced. L and S values were assigned tentatively by us to many of these terms; but changes in some of the values were suggested later by Symons and Daley after they had carried out a Zeeman effect analysis of gold arc lines.