Regularities in the spectra of lutecium

Abstract

Up to the present time no significant regularities have been found in the spectra of any of the lare earth elements, 58 Ce to 71 Lu. A study of the arc and spark spectra of the last of these, lutecium, resulted in a separation of the lines into three distinct classes: (1) Those characterizing neutral atoms, constituting the Lu spectrum; (2) those due to singly ionized atoms, the Lu" spectrum; and (3) a small number of lines ascribable to doubly ionized atoms, the Lu ITI spectrum. Regularities have been discovered in each of these spectra. The normal state of neutral Lu atoms is represented by a 2 D spectral term arising from the electron configuration s 2 d; its levels are separated by 1993.9 wave numbers. The normal state of Lu + atoms is described by a ! S (ss), and metastable terms 1 D, 3 D (ds), 3 F (dd) have also been established. A 2 S (s) term describes the normal state of Lu ++ atoms. There is no evidence of / electrons playing any part in the production of the spectra; it is concluded that the fourteen / electrons in Lu form a closed shell of considerable stability. The structures of Lu spectra resemble those of Y more closely than those of La or Sc. CONTENTS Page I . Introduction 73 II. The spectrum of neutral Lu (LuJ 75 III. The spectrum of singly ionized Lu (Lu ri ) 77 IV. The spectrum of doublv ionized Lu (Lu",) 79 V. Comparison of 21 Sc, 39 Y, 57 La, and 71 Lu spectra 79