The band spectrum of nitrogen sulphide (NS)

The present investigation had its origin in an observation by one of us that in a vacuum tube containing sulphur vapour with an impurity of nitrogen, there appeared a previously unrecorded band spectrum which bore a striking resemblance to that of nitric oxide (NO). As only sulphur and nitrogen were known to be present, this similarity suggested that the new spectrum might be due to nitrogen sulphide (NS), since oxygen and sulphur have the same number of valence electrons. This supposition appears to be fully confirmed by the further experiments which have been made and by the vibrational analysis of the bands. The principal members of both sets of bands occur in the ultra-violet and nearly in the same region. It will be convenient first to give a brief account of the bands of nitric oxide.The Bands of Nitric Oxide . The principal bands of NO are well known from their occurrence in air vacuum tubes; they were long ago named the “Third Positive Bands of Nitrogen” by Deslandres, who, nevertheless, considered that the presence of both nitrogen and oxygen was necessary for their production. These bands were observed by Fowler and Strutt (now Lord Rayleigh) to appear in the spectrum of the nitrogen afterglow, and the opinion was expressed that nitrogen alone was capable of producing them. Subsequent work by Lewis and by Strutt,§ however, supported the view that the bands were produced only when both nitrogen and oxygen were present. During the present investigation, also, it has been found that the bands in question do not occur in vacuum tubes containing nitrogen when oxygen has been completely removed. These experimental results are in agreement with the conclusion derived from analyses of the band structure that the bands originate in the diatomic molecule NO.