The Infrared Spectrum of Sn I

An open arc of 80 amperes between a carbon rod and tin pool has been used as source, and observations have been made using a grating spectrometer and thermopile. The wave-lengths of forty-five new lines of the tin arc spectrum in the region from 1{μ} to 3{μ} have been measured, and rough determinations of the relative intensities of the strong lines have been made. Nine energy levels of the 5s²5p6p configuration have been found, which with the one found by Green and Loring complete the set. Three of the four levels of the 5s²5p(²P1/2)4f set have been found, and the fourth,3₃, has been accounted for as lying too close to 4₂ for resolution. With the fixing of these levels all the strong infra-red lines have been classified. The finding of the levels 5p(²P1/2)4f4₂ and 5p(²P1/2)5f4₂ has made possible a good determination of the absolute term values.