J dependences of the isotope shift and hyperfine structure in Gd I 4f75d6s29D, 4f75d6s6p 9D, and 9F terms

Isotope shifts of 16 transitions in 4f75d6s2(9D)-4f75d6s6p(9D,9F) of Gd I for the stable isotopes with A=152--160 were measured by atomic-beam laser spectroscopy. The hyperfine constants A and B of 155Gd and 157Gd in two 9D terms and the 9F term were determined. The single-electron hyperfine parameters a4f10 for the 4f electron and a5dkskl,b5dkskl for the 5d electron were deduced. The electric quadrupole moments Q of 155Gd and 157Gd were obtained to be 1.27(5)b and 1.36(6)b, respectively. The J dependences of the isotope shifts in two 9D terms and the 9F term were observed. The parameter z5d of the crossed-second-order effect for the 9D term of 4f75d6s2 was derived, and the value of z5d/λ was obtained to be 134(4) MHz/fm2. We confirmed that the field shift is dominant in the crossed-second-order effect and the specific mass shift is negligible