Temperature Classification of the Spectrum of Neodymium

The paper gives the temperature classification of 2863 neodymium lines in the spec- tral range XX 2963-7005, based on their relative intensities at three temperature stages of the electric furnace. The neutral spectrum, strong in the furnace, includes many lines that are faint in the arc, especially in the shorter wave-length region, a large proportion of which are now measured for the first time. The spectrum is notable for the large num- ber of lines in classes I and II, which are well developed at 2000° C, while the neutral lines in higher classes appear near 23000. The classification includes also the stronger lines of singly ionized neodymium, selected by comparing the furnace spectra with those of the arc and spark. A majority of these enhanced lines are present in the furnace spectrum at 2600°. Wave-lengths of 2026 lines were measured, comprising new neutral lines and others for which improved wave-lengths could be obtained. The dominance of the lines of Nd i, Nd it, and Nd iii in different spectral ranges is discussed. A comparison of neodymium spectrograms with those of samarium was made with reference to lines apparently common to both spectra, which might belong to the inter- mediate element 61. Lines of this character given by the samples used in this investiga- tion appear, however, to result from chance coincidences of true neodymium and samarium lines