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 1μ to 3μ have been measured, and rough determinations of the relative intensities of the strong lines have been made. Nine energy levels of the $5s^{2}5p6p$ configuration have been found, which with the one found by Green and Loring complete the set. Three of the four levels of the $5s^{2}5p\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)4f$ set have been found, and the fourth,$3_3$, has been accounted for as lying too close to $4_2$ for resolution. With the fixing of these levels all the strong infra-red lines have been classified. The finding of the levels $5p\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)4f{4}_2$ and $5p\left({}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\right)5f{4}_2$ has made possible a good determination of the absolute term values.