Nd I and Nd II spectra emitted by an electrodeless tube have been observed between 2450 and 40 500 Å. By means of 25 000 wavelengths measured with an automatic comparator and of the Zeeman patterns of the strongest lines, about 1500 energy levels have been found. Their interpretation was carried out with the use of isotopic-shift data and empirical parametric calculations. The present state of the classification is described. The main features of the 15 known configurations and some results of theoretical calculations are given.
J. BLAISE, J. F. WYART, R. HOEKSTRA, and P. J. G. KRUIVER, "Present State of the Analysis of Nd I and Nd II," J. Opt. Soc. Am. 61, 1335-1342 (1971)