HYPERFINE QUENCHING AND PRECISION-MEASUREMENT OF THE 23P0-23P1 FINE-STRUCTURE SPLITTING IN HELIUM-LIKE GADOLINIUM (GD62+)

The hyperfine-quenched transition 2P-3(0)-1S-1(0) has been observed in heliumlike gadolinium (Gd62+) in the two isotopes Gd-155 and Gd-157. The lifetime for the transition (tau-0) has been measured for each isotope and found to be tau-0(155) = 13.43(27) x 10(-12) sec and tau-0(157) = 7.65(55) x 10(-12) sec. From the measured lifetimes a value is inferred for the absolute value of the 2P-3(0)-2P-3(1) fine-structuring splitting \DELTA-E0-1\ in Gd62+ with the result \DELTA-E0-1\ = 18.57(19) eV, where the error represents 1 standard deviation. This result is compared with calculations based on the multiconfiguration Dirac-Fock method and on the unified method.