Quadrupole moments of yrast isomers in 144, 147, 148Gd

Abstract Isomeric nuclei of 144, 147, 148 Gd were produced by 120, 124 Sn ( 28 Si , x n ) fusion evaporation reactions and implanted into single crystals of Gd. The perturbed angular distribution spectra at various orientations of the crystal axis are dominated by static quadrupole interactions. The ratio of quadrupole moment Q to spin I was determined for the 10 + isomer in 144 Gd, the 13 2 + , 27 2 − and (T 1 2 = 510 ns ) isomers in 147 Gd, and the 9 − isomer in 148 Gd. In addition a tentative value of I = ( 47 2 ± 1) was obtained for the spin of the 510 ns isomer in 147 Gd. The observed quadrupole moments provide the first experimental evidence for the substantial oblate deformation ( β ∼ −0.2) predicted by the deformed independent particle model of Neergard, Dossing and Sagawa for high-spin isomers in 147 Gd. The oblate deformation is observed to increase when the number of valence nucleons (and the isomer spin) increases, and furthermore when the neutron core at N = 82 is broken. The g -factors and quadrupole moments of the 3 − and 10 + core states in 146 Gd have also been deduced.