Accurate wavelengths and wavenumbers of over 22 000 dysprosium lines have been measured in the wavelength region 2300-11 400 Å. The Zeeman effect has been observed at a field strength of 24000 G from 2300 to 9000 Å. By comparison of relative intensities of the lines from sources under various conditions, 85% of the lines have been assigned as Dy I or Dy II spectrum lines. From the energy-level analysis, 141 even and 197 odd levels of Dy I are known. Combinations between these levels account for 1952 lines. For Dy II, 14 even and 214 odd levels are known, with 1000 lines classified. The ground levels of Dy I and Dy II are 4ƒ<sup>10</sup>6<i>s</i><sup>2</sup><sup>5</sup><i>I</i><sub>8</sub> and 4ƒ<sup>10</sup>6<i>s</i><sup>6</sup><i>I</i><sub>8</sub><sub>½</sub>, respectively. The lowest level of the 4ƒ<sup>9</sup>5<i>d</i>6<i>s</i><sup>2</sup> configuration of Dy I lies 7565.62 cm<sup>-1</sup> above the ground level. The <i>g</i> values for most of the levels of both spectra are given.
JOHN G. CONWAY and EARL F. WORDEN, "Preliminary Level Analysis of the First and Second Spectra of Dysprosium, Dy I and Dy II," J. Opt. Soc. Am. 61, 704-726 (1971)