Gyromagnetic ratios of excited states in186W

Abstract

The gyromagnetic ratios of the 4[, 6 3, and 2 7 states in ls6W were measured relative to that of the 2 7 level by means of the transient field implantation perturbed 7-ray angular distribution technique. The nuclei in the states of interest were Coulomb excited using a beam of 220-MeV 63Cu projectiles and recoiled swiftly through a thin, polarized Fe foil.The present measurements yielded ratios g(4[)/g(2~)=l.04_+0.07, g(6~-)/g(2~-)=1.03 _+0.20 and g(2~-)/g(2~-)=0.63_+0.13. The sizable disparity between the measured gfactors of the ground-and excited-band is examined within the context of the interacting boson approximation model.

Disparity of measured gyromagnetic ratios of ground- and excited-band states in184W

“…Nonetheless, it is of some importance to recognize, as have Wood and Morrison [4], that the model reproduces energy level spectra and dominant B(E2) decays by construction (i.e., fitting parameters and subgroup chains); as such, comparisons of model fits with E2 observables and level spectra may not provide particularly incisive tests of the model's validity or degree of approximation {e.g., the role of nonbosonic degrees of freedom and the degree of noncollective to collective (boson) coupling are not obtained readily from B(E2) fits [4]}. On the other hand, our recent studies [5,[6][7][8][9][10][11], wherein IBMbased calculations of gyromagnetic ratios of excited states in Pt, Os, and W isotopes have been compared with measured values and critically assessed, have questioned the consistency of standard IBM energy level and B(E2) fits when combined with gfactor predictions. Principally through these works, experimental and theoretical interest and emphasis have been focussed on the M1 observables [B(M1) rates and gyromagnetic ratios] which appear to provide much better tests of the model; this is especially so for g-factor determinations which probe the structures of individual states.…”

Disparity in transient field characteristics for Au ions traversing Fe and Gd hosts through measurements ofg-factors in197Au

“…Our results for W and Au ions simultaneously traversing Fe hosts were obtained, in part, during our study [11,12] of the g-factors of levels in 186W.…”

“…While the extraction of the relative gyromagnetic ratios of levels in 197Au from the simultaneously measured TF precessions is rather straightforward [12][13][14]22], to obtain absolute g-factors of states in 197Au from the observed precession angles requires knowledge of the behaviour (velocity-dependent magnitude) of the TF for Au ions recoiling through the particular ferromagnetic host. In earlier publications [5,6,8] we discussed the abrupt discontinuity in TF strength which occurs between 76Os and 7sPt ions traversing polarized Fe hosts with velocities ~ 0.02 c. In contrast with TF studies using Fe hosts, no discontinuities [20,21].…”

“…Although the measured g-factors of the corresponding low-lying levels of the stable even lsz'~s4'~s6w isotopes are not the same, previous measurements [12,13,23] have established that the gfactors of the low-lying levels in the ground-band of any particular one of these isotopes are identical within experimental uncertainties. As the presence of these isotopes in the target was for the purpose of calibrating the TF strength, there was neither any advantage nor need to extract the separate contributions to the observed (re d) precessions of the individual g s b levels in any given even W isotope studied.…”

“…Such simultaneous measurements largely obviate possible sources of systematic errors. For the calibration of the TF strength in polarized Gd hosts, the known g-factors [8,12,13,16] of states in the even W isotopes were chosen, in preference to reliance upon the g-factors [5][6][7] of states in the even Pt nuclides which were the subject of the controversy noted above.…”