Measured gyromagnetic ratios of individual excited states in the ground- and gamma-bands of166Er

Abstract

The gyromagnetic ratios of levels up to the 10 + in the ground-state band and of the 2+ state in the y-band of 166Er were simultaneously determined experimentally by means of the thin-foil, perturbed y-ray angular distribution technique utilizing the transient hyperfine field manifest at nuclei of Er ions rapidly traversing polarized Fe. Beams of 220-and 160-MeV 58Ni projectiles were used to Coulomb excite the levels of interest. The present results are compared with the spin-dependencies of g-factors of levels in the ground-band predicted by recent cranked Hartree-Fock-Bogoliubov calculations and with interacting boson model expectations which include g-boson effects.

Gyromagnetic ratios of 4+ and 6+ states in156Gd and158Gd

“…It should be mentioned, however, that in the case of the even-even erbium isotopes recent self-consistent cranked Hartree-Fock-Bogoliubov (HFB) calculations by Sugawara-Tanabe (University of Tokyo) and Tanaba (Saitama University) [38] nicely reproduce the fast decrease of g(l) observed for 166Er [10,13], the constant behaviour of g(I) observed for a68Er [12] and a g-factor close to zero at I= 16 + for a58Er [39]. Simultaneously these calculations give hCOro t as a function of the spin I of the ground-state rotational bands up to the region of the first backbending in good agreement with the experimental data for all even-even erbium isotopes between A=158 and A= 170.…”

Gyromagnetic ratios of low-lying rotational states in156, 158, 160Gd

“…The gsb g-factors have been observed to diminish significantly with increasing spin in the N = 98 isotone 166Er [12,8] (and perhaps also in 164Dy [13]). In these N = 98 nuclei the mechanism for the pronounced spindependent reduction in the g-factors is the well-known strong interaction between the ground-band and the aligned (i13/2) 2 s-band [10,11].…”

“…Experimental procedures followed were similar to those described previously [5][6][7][8]. Levels of interest in 156, as8, X60Gd were populated by Coulomb excitation using 160 MeV 5SNi beams from the Australian National University 14UD Pelletron accelerator.…”

“…Procedures employed to extract g-factors from measured TF precessions, in which account is taken of the effects of cascade feeding and decay-in-flight corrections have been outlined in several earlier publications [5][6][7][8]. In the present work the corrections for decay in flight proved negligible as all levels of interest have lifetimes much longer than the transit time of the Gd ions through the Fe foil.…”

“…Corrections to the observed precessions for the effects of cascade feeding require knowledge of the relative direct populations of the levels. These were measured for the 4+ and higher levels by our usual procedures [6][7][8]. For the 2+ states, however, which decay by low-energy transitions (75 to 89 keV) and undergo significant angledependent absorption in the target layers, the energyefficiency determined using calibrated 7-ray sources was not relied upon.…”