Temperature Classification of the Spectra of Europium, Gadolinium, Terbium, Dysprosium, and Holmium, λ 3850 TO λ 4700

Abstract

Spectra of europ'ium, gadolinium, terbium, dysprosium, and holmium, as given by electric furnace, arc, and spark, have been examined in the range A 3850 to X 4700 with regard to the segregation of neutral and enhanced lines, temperature classification, the occurrence of /iyperfine structure, and other distinctive features. The total of 2277 lines listed is made up of 219 lines of europium, 627 of gadolinium, 733 of terbium, 534 of dysprosium, and 164 of holmium. Measurements of wave-length were made for 666 lines. These are in part new lines prominent in the furnace but faint in the arc spectrum, partly known lines for which improved measurements could be obtained, and partly close doublets previously meas- ured as singk lines. The spectra of gadolinium, ter&ium, and dysprosium are especiafly rich in neutral lines which are relatively strong in the furnace. Europium and dysprosium show low- temperature lines which have high intensity and are easily reversible, a type which 3 unusual in the spectra of the rare earths. Lines having hyperfine structure are numerous in the spectra of europium, terbium, and holmium. The patterns of hyperfme holmium lines resemble those of praseo- dymium. The present material, taken in connection with data at hand for other rare earths, shows that hyperfine structure occurs regularly in the spectra of rare earths of odd atomic number, as far as their spectra have been observed with reference to this phenomenon, while for even numbered rare earths the spectrum lines are uniformly without hyperftne structure