Transient-field strength measurements for52Cr traversing Fe hosts at high velocity and polarization transfer mechanisms

Transient-field strengths were measured for⁵²Cr ions traversing polarized Fe hosts at velocities up to 12υ₀ (12υ₀ =c/137 = Bohr velocity). The results are compared with predictions of various transient-field parametrizations and discussed in terms of possible mechanisms by which polarization might be transferred from the Fe host to inner vacancies of the moving Cr ions. Theg-factor of the first 2⁺ state of⁵²Cr was also measured by the transient-field technique and found to be in accord with shell model calculations.     

Preparative isolation of (+)-beta-eudesmol fromAmyris balsamifera

Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum distillation of the total oil. Step two was a medium pressure LC separation with an AgNO₃ impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related sesquiterpene alcohols (75% of the oil).     

Measured static hyperfine magnetic fields following implantation of Pt into Fe interpreted as evidence for pre-equilibrium effects

The static hyperfine magnetic field present at Pt nuclei implanted in ferromagnetic Fe has been measured using the ion-implantation perturbed angular correlation (IMPAC) technique following Coulomb excitation. The present measured precessions agree with earlier data, but more recent information on the transient field correction leads to an inferred static field strength that is 25% smaller than obtained previously. Comparisons are made between the static fields measured by various techniques for Pt and neighbouring ions in iron. From these comparisons, we show that the IMPAC data are consistent with a scenario in which (i) the static field takes about 10 ps to reach its equilibrium value, following recovery from dynamic structural damage caused by the ion-implantation process, and (ii) following equilibration, a large fraction ( 90%) of the implanted ions have final positions on lattice sites of the Fe host.     

Gyromagnetic ratios of excited states in186W

The gyromagnetic ratios of the 4 ₁ ⁺ , 6 ₁ ⁺ , and 2 ₂ ⁺ states in¹⁸⁶W were measured relative to that of the 2 ₁ ⁺ level by means of the transient field implantation perturbedγ-ray angular distribution technique. The nuclei in the states of interest were Coulomb excited using a beam of 220-MeV⁶³Cu projectiles and recoiled swiftly through a thin, polarized Fe foil. The present measurements yielded ratiosg(4 ₁ ⁺ )/g(2 ₁ ⁺ )=1.04±0.07,g(6 ₁ ⁺ )/g(2 ₁ ⁺ )=1.03 ±0.20 andg(2 ₂ ⁺ )/g(2 ₁ ⁺ )=0.63±0.13. The sizable disparity between the measuredg-factors 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

Gyromagnetic ratios of levels in the ground-band and of the 2 ₂ ⁺ state in¹⁸⁴W were measured by means of the transient magnetic field perturbedγ-ray angular distribution technique. The levels of interest were Coulomb excited by beams of 220-MeV⁵⁸Ni and⁶³Cu ions. The results show theg-factor of the 2 ₂ ⁺ state to be approximately half the effectively constant value found for the ground-band levels. This disparity is compared with those previously obtained for the corresponding states in^188–192Os and¹⁸⁶W; these are discussed in the context of the interacting boson model.     

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

Transient-field precessions were measured simultaneously for levels in the ground-state bands of^{156, 158, 160}Gd as ions of these nuclei traversed a thin polarized Fe foil. Relative g-factors of levels up to 6 ₁ ⁺ were deduced, those of the 4 ₁ ⁺ levels being determined with greatest precision. In contrast with the conclusions of the recent report by Alzner et al. [1], our results are consistent with g(4 ₁ ⁺ ) having the same value in all three isotopes and imply g(2 ₁ ⁺ )=g(4 ₁ ⁺ ) in¹⁵⁶Gd, consistent with nuclear structure models.     

Measured lifetimes of states in 197Au and a critical comparison with the weak-coupling core-excitation model

The lifetimes of five excited states in ¹⁹⁷Au up to an excitation energy of 885 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV ²⁰Ne and 120 MeV ³⁵Cl ion beams. The experimentally determined spectroscopy of the low-lying levels $\text{3}\text{2}{}^{\mathrm{+}}$ (ground state) and $\text{1}\text{2}{}^{\mathrm{+}}$, $\text{3}\text{2}{}_2{}^{\mathrm{+}}$, $\text{5}\text{2}{}^{\mathrm{+}}$, and $\text{7}\text{2}{}^{\mathrm{+}}$ at 77.3, 268.8, 278.9, and 547.5 keV excitation energy, respectively, has been critically compared with the detailed predictions of the de-Shalit weak-coupling core-excitation model. When the model is taken to represent the case of a $\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ proton hole coupled to a ¹⁹⁸Hg core, the model parameters obtained are in accord with the criteria implicit for weak core coupling and, at the same time, are in remarkably good agreement with virtually all measured E2 and M1 transition rates.     

Level structure and lifetimes of low-excitation states in 63Cu

The lifetimes of 9 states in ⁶³Cu up to an excitation energy of 2092 keV have been determined by means of the Doppler-shift attenuation method using the ${}^{60}\text{Ni}\text{(α,}\text{p}\text{γ)}$ reaction. A search was made for a suitable set of M1 and E2 single-particle matrix elements for use with shell-model eigenstates throughout the Ni, Cu and Zn isotopes. The theoretical predictions for the level spectroscopy and electromagnetic transitions and static moments in ⁶³Cu are in satisfactory agreement with the experimental findings.     

High-spin g factors and proton alignment in Pt

The average g factors of high-spin states in ^180,182,184Pt were measured by the transient-field technique. In all three isotopes the quasicontinuum g factor at an angular momentum of 20 is g0.37. This contrasts with similar measurements on other nuclei that have 70Z80, where typical values of g0.22 have been attributed to the influence of quasineutron alignments. Evidently proton and neutron configurations are about equally important at high spin in the Pt isotopes near mid-shell. This inference is consistent with the discrete spectroscopy, including the contention, supported by g_K−g_R values, that h_9/2 proton pairs align along with the i_13/2 neutrons at rotational frequencies of ω≈0.3 MeV in ¹⁸⁴Pt. Links between the quasicontinuum g factors and features in the discrete spectroscopy are explored by comparing and contrasting the behavior of ¹⁸⁴Pt and ¹⁶⁶Hf.     

Systematic measurements of transient fields for W,Os and Pt ions traversing Fe

Transient magnetic fields were measured for W, Os and Pt ions traversing iron hosts with average velocities in the range from approximately 1.6v ₀ to 4.8v ₀ (v ₀=c/137, Bohr velocity). Transient fields for W and Os in Fe are consistent with behaviour found for lighter rare-earth ions and are about 20% stronger than those for Pt in Fe over the majority of the velocity range examined. A measurement was made to confirm that possible heavy-ion beam induced attenuations of the transient field are negligible for low-velocity Pt ions excited by Ni beams. Results are discussed in terms of both empirical and model-based parameterizations of the transient field strength.