The Classification of the Spectrum of Singly Ionized Tin. Sn II

Abstract

The spectrum of Sn II, as excited in a hollow cathode discharge in helium, has been photographed from 800A to 10,000A. Some 70 new lines have been classified and 28 new levels established. A few changes have been made in the levels and classifications previously made by Green and Loring, Narayan, and Lang. The $5{s}^{2}\mathrm{ms}$, $\ensuremath{-}mp$, $\ensuremath{-}md$ and $\ensuremath{-}mf$ series have been extended, and the $^{2}F$ levels have been resolved for the first time. Six members of the $5{s}^{2}\mathrm{mg}$ $^{2}G$ series have been located and used to make a new determination of the ionization potential of Sn II as 118,017\ifmmode\pm\else\textpm\fi{}3 ${\mathrm{cm}}^{\ensuremath{-}1}$. The classification has been checked by series relations, Zeeman patterns, and by comparison with the isoelectronic spectra In I and Sb III. Irregularities in the $^{2}S$ and $^{2}D$ terms are explained qualitatively by consideration of interactions with perturbing terms from the configuration $s{p}^{2}$.