D. Ward

Stopping power measurement for 19F, 24Mg, 27Al, 32S and 35Cl at energies ∼0.2 to ∼3.5 MeV/nucleon in Ti, Fe, Ni, Cu, Ag and Au

Abstract Stopping powers have been measured for beams of 19 F, 24 Mg, 27 Al, 32 S and 35 Cl for energies ∼0.2 to ∼3.5 MeV/nucleon in Ti, Fe, Ni, Cu, Ag and Au to an accuracy of ±4%. The results are compared with previous experimental values and with the semiempirical tabulation of Northcliffe and Schilling. A stopping power table for these six materials containing all projectiles in the range 8 ≤ Z ≤ 20 is presented.

Gamma decay of low-lying states near the 208Pb closed shell

Abstract A number of electromagnetic matrix elements between low-lying states of several nuclei near 208Pb have been measured. Coulomb excitation of states in 204, 206, 207, 208pb and 209Bi has been studied with beams of 4He and 16O. The energy loss of 4He and 16O in Pb has been measured by a novel method and thus accurate B(E2) and B(E3) values were obtained. Gamma-ray lineshapes observed after 16O bombardment were used to derive mean lifetimes of states at 2646.5 keV (τ = 0.125±0.030 ps) in 206Pb, and at 897.7 keV (τ = 0.19±0.04 ps), at 2624.4 keV (τ = 0.13±0.05 ps), and at 2662.4 keV (τ = 0.95±0.20 ps) in 207Pb. The reactions 208pb(7Li, α2nγ)209Bi and 208Pb(7Li, 6Liγ)209Pb were used for the first time to derive several lifetimes and branching ratios in 209Bi and 209Pb. An intermediate-coupling calculation has been performed which reproduces extremely well the known B(E2) values in 207, 208Pb and 209Bi and which qualitatively explains the observed E1 matrix elements. Evidence for retardation of single-particle M1 transitions is presented. The main cause for the retardation is excitations of spin-orbit partners. Possible contributions from higher-order excitations and from mesonic exchange currents are discussed.

Quadrupole Moment of a High-Spin Yrast Trap in Gd 147

Static quadrupole interactions of three

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

^{147}\mathrm{Gd}

High spin yrast states in N = 126 isotones

isomers in single crystals of hexagonal gadolinium have been observed. The quadrupole moments increase with increasing spin and imply a substantial (oblate) deformation (

Yrast isomers and very high spin states in 148, 149, 151, 152Dy and 147Gd

\ensuremath{\beta}\ensuremath{\sim}0.2

Calibration of the transient magnetic field for rare-earth nuclei in iron: Application to g-factors of high spin states in 152, 154Sm

) for the 500-ns high-spin yrast trap.

Co-existence of spherical and oblate configurations in 147Gd

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.

Magnetic moments of N = 50 isotones and proton core polarization

Abstract A comprehensive spectroscopic investigation of yrast levels in three N = 126 isotones, 212 Rn, 213 Fr and 214 Ra, is presented. We report measurements of prompt and delayed excitation functions, γ-γ and X-γ coincidences, g -factors, linear polarizations and angular distributions of γ-rays. Yrast spectra in these nuclei extend to high spin and are rich in isomers. The isomerism and the spin dependence of yrast energies for N = 126 isotones are discussed in terms of excitations of valence protons with and without contributions from the 208 Pb core.

Measurement of lifetimes for high spin states in 152Sm, 154Gd and 156Gd by the Doppler broadened lineshape method

Abstract We have studied level schemes for the feeding and decay of high-spin isomers in the nuclei 148, 149, 151, 152 Dy and 147 Gd. A variety of techniques involving γ-ray spectroscopy with pulsed heavy-ion beams have been applied including linear polarization, γ-γ correlations and recoil distance measurements. The general aspect of these level schemes is in accordance with the idea that the states near and along the yrast line can be described by a spheroidal shell model in which the nucleus is axially symmetric with respect to the total spin. In these cases the spin is generated not by collective rotation, but by alignment of many single-particle orbits around a common axis.