The isotope shift in the 7 2S½ - 6 2P½ transition (3776 Å) and the hyperfine-structure separations of Tl203 and Tl205 in the 7 2S½ state have been determined spectroscopically by atomic beam absorption with the use of a Fabry—Pérot interferometer crossed with a 10-in. diffraction grating. Our results are: 0.0554±0.0012 cm-1 for the isotope shift in the 3776 Å line; -0.0405±0.0013 cm-1 in the 6 2P½ level; and Δν (7 2S½)=0.4078 ±0.0014 cm-1 and 0.4109±0.0012 cm-1 for the hyperfine-structure separation in Tl203 and Tl205, respectively.
C. J. SCHULER, M. ÇIFTAN, L. C. BRADLEY, III, and H. H. STROKE, "Hyperfine Structure and Isotope Shift in the 7 2S½ - 6 2P½ Transition of Natural Thallium by Atomic Beam Absorption," J. Opt. Soc. Am. 52, 501-503 (1962)