The NH Band and the Dissociation Energy of Nitrogen

Abstract

THE so-called ammonia band at 3360–70 A., photographed first by Eder in 1892, has since been studied and measured by many authors. Fowler and Gregory (Phil. Trans. Roy. Soc., 218, 351; 1919) have published beautiful photographs of it. Lately this band has been attributed by Barrat (Proc. Roy. Soc., A, 98, 40; 1920), Hulthen and Nakamura (NATURE, 119, 235; 1927), and others to the NH molecule. Using R. W. Wood's arrangement for the optical excitation of mercury vapour (Phil. Mag., Oct. 1925, Sept. 1927), I have observed the appearance of it when about 4 mm. nitrogen and very little hydrogen—perhaps a few thousands of mm.—are admitted to the quartz tube containing the mercury vapour which is being excited by the light of a water-cooled, magnetically deflected mercury arc.