High-resolution spectra of a <sup>232</sup>ThI<sub>4</sub> / <sup>230</sup>ThI<sub>4</sub> electrodeless discharge lamp were obtained from 5600 to 36000 cm<sup>-1</sup> with a Fourier-transform spectrometer. The splittings of more than 2800 Th I isotopic doublets were measured to an accuracy of 0.001 cm<sup>-1</sup>. Level isotope shifts were determined for 274 even and 318 odd levels of Th I.
© 1983 Optical Society of America
R. Engleman, Jr. and B. A. Palmer, "Precision isotope shifts for the heavy elements. II. Neutral thorium," J. Opt. Soc. Am. 73, 694-701 (1983)