J dependence of the isotope shift in the GdI 4f(7)6s(2)6p(9) P term

High-resolution laser spectroscopy in Gd I has been performed using a tunab le diode laser. Isotope shifts of the even-mass isotopes have been measured for two transitions from the 4 f(7) 5d6s(2) D-9(4) and D-9(5) levels to th e 4 f(7) 6s(2)6p P-9(3) and P-9(4) levels in Gd I. The J dependence of the isotope shift. related to the crossed-second-order (CSO) effect, has been o btained for the 4 f(7) 6s(2)6p P-9(3) and P-9(4) levels. The CSO parameter Z(6p) of the 4 f(7)6s(2)6p configuration has been estimated for the first t ime.