Hyperfine structure and isotope shift of the 6s6p24P½ level of Tl I

The h. f. s. splittings and isotope shifts have been measured for the transition 6s26p 2P0½–6s 6p2 4P½ in Tl203, Tl205. These are the largest splittings occurring in the levels of Tl I. The results agree in order of magnitude with splittings and shifts to be expected theoretically. The quartet level perturbs the n = 10 member of the 6s2ns2S½ series, which consequently acquires a large splitting and a measurable shift.