Measurement of the g factors of isomers near the proposed N ≈ 40 subshell closure

We report results from a pioneering experiment to measure the g factors of isomeric states of neutron-rich nuclei around ⁶⁸Ni, far from the valley of β stability.For the first time, the time-dependent perturbed angular distribution method was applied in combination with the heavy-ion-γ correlation technique to study g factors of spin-aligned isomers produced in a projectile fragmentation reaction and mass-separated. Some technical aspects are discussed and illustrated with preliminary results.     

A new measurement of the Li(d,p)Li cross section and consequences for Be(p,γ)B

A novel scheme for measuring the cross section of the ⁷Be(p,γ)⁸B reaction, the major source of high energy neutrinos from the sun, is presented. The scheme involves a strictly uniform particle beam and overcomes some of the recognized experimental uncertainties of previous measurements. A new measurement of σ[⁷Li(d,p)⁸Li] has been carried out using this setup, and the present value of σ[⁷Li(d,p)⁸Li] = 155(8) mb at the top of the E_d(lab.) = 776 keV resonance is compared with previous measurements. A new issue regarding both the (d,p) and (p,γ) reactions has been examined: reaction-product nuclei which are backscattered out of the target. Measurements and simulations carried out in the course of this investigation are presented and discussed in the context of possible effects on the measured cross sections of these reactions.     

The magnetic moment of the first-excited 2+ state in 18O

The magnetic decoupling method, applied to highly ionized nuclear-excited ¹⁸O atoms, has yielded for the 198 MeV 2⁺ state the value |g| = 0.35 ± 0.04. In conjunction with the recently determined negative sign, this value agrees well with weak j-j coupling predictions.     

Magnetic moment of the fragmentation-aligned 61Fe (9/2(+)) isomer

We report on the g factor measurement of an isomer in the neutron-rich (61)(26)Fe (E(*)=861 keV and T(1/2)=239(5) ns). The isomer was produced and spin aligned via a projectile-fragmentation reaction at intermediate energy, the time dependent perturbed angular distribution method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the nuclear spin ensemble has been observed, allowing a precise determination of its g factor, including the sign: g=-0.229(2). In this way we open the possibility to study moments of very neutron-rich short-lived isomers, not accessible via other production and spin-orientation methods.     

Dynamics of the w function and primes

We begin by defining a function w on the set

     

Precision measurement of the 7Be(p,gamma)8B cross section with an implanted 7Be target

The 7Be(p,gamma)8B reaction plays a central role in the evaluation of solar neutrino fluxes. We report on a new precision measurement of the cross section of this reaction, following our previous experiment with an implanted 7Be target, a raster-scanned beam, and the elimination of the backscattering loss. The new measurement incorporates a more abundant 7Be target and a number of improvements in design and procedure. The point at E(lab)=991 keV was measured several times under varying experimental conditions, yielding a value of S17(E(c.m.)=850 keV)=24.0+/-0.5 eV b. Measurements were carried out at lower energies as well. Because of the precise knowledge of the implanted 7Be density profile, it was possible to reconstitute both the off- and on-resonance parts of the cross section and to obtain from the entire set of measurements an extrapolated value of S17(0)=21.2+/-0.7 eV b.     

The magnetic moment of the first excited state of 19O

The magnetic moment of the first excited 96 keV, $\text{3}\text{2}{}^{\mathrm{+}}$ state of ¹⁹O has been determined by an integral perturbed angular correlation measurement in a transverse external magnetic field. The value obtained for the g-factor, ?0.48(6), is discussed in terms of shell-model configurations. The wave function of the $\text{3}\text{2}{}^{\mathrm{+}}$ level is shown to consist mainly of the $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^3$ configuration.