High-resolution Fourier-transform spectra of a 232ThI4–230ThI4 electrodeless discharge lamp were obtained between 5600 and 36 000 cm−1. These spectra were used to measure the splittings of more than 800 isotopic Th II doublets to an accuracy of about 0.001 cm−1. From these isotope shifts, 184 even- and 167 odd-level isotope shifts were determined. Level isotope shifts were determined for all known levels below 20 000 cm−, except for the even J = ½ level at 19 594 cm−1. An empirical correlation of the level isotope shifts with a theoretical, configuration-mixing calculation was used to derive pure-configuration level isotope shifts.
© 1984 Optical Society of America
Rolf Engleman, Jr. and Byron A. Palmer, "Precision isotope shifts for the heavy elements. III. Singly ionized thorium (Th II)," J. Opt. Soc. Am. B 1, 782-787 (1984)