The λ 2530 band of NH

Abstract

A previous communication by the authors described the use of a hollow cathode discharge in rapidly streaming ammonia for the excitation of a new band system of NH having its (0, 0) band at λ 4502. Observations of the spectrum obtained under these conditions have now been extended to the ultra-violet region. With an improved hollow cathode capable of carrying heavier currents, in addition to the well-known bands of the 3 Π → 3 ∑ and 1 Π → 1 ∆ systems of NH, a band is obtained at λ 2530 identical with that reported bx Hori. Hori used a 40 kV transformer discharge in a mixture of nitrogen and hydrogen between a wire and a cup-shaped electrode of tungsten, the cup containing sodium or lithium. The intensity of the band was extremely weak compared with that in the hollow cathode discharge, which is such that the band max be photographed on a Hilger E1 quartz spectrograph with exposures of from 1 to 2 hours. The examination of the band as seen under higher dispersion than that used by Hori confirms his assignment of the band to the molecule NH; it also allows the authors to correct certain details of Hori's analysis, and to relate the band to bands of NH which are already known. Table I contains all the lines measurable in the region of the band. The strong lines are nearly all accounted for by the P, Q, and R branches of the λ 2530 band, the (0, 0) band of the system. A number of the remaining weaker lines have been assigned to the P, Q, and R branches of the (1, 1) band, as indicated in italics in the table.