G. Goldring

Solar fusion cross-sections

We review and analyze the available information on the nuclear-fusion cross sections that are most important for solar energy generation and solar neutrino production. We provide best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties. We also describe the most important experiments and calculations that are required in order to improve our knowledge of solar fusion rates.

Hyperfine interaction studies of heavy nuclei in highly ionized atoms

Abstract A detailed and extensive study of the hyperfine interaction of nuclei with highly ionized atoms in gas is reported. Some new and unexpected features of the interaction are discussed. These relate to the pressure dependence of the perturbation, its variation with Z and dependence on recoil velocity; g -factors of 2 + levels were determined for nuclei in the mass range: 148 ≦ A ≦ 190.

Precession measurements following Coulomb excitation with oxygen ions (VI). Hyperfine interactions of nuclei in highly ionized atoms

Abstract Measurements are reported of angular distributions of gamma rays from excited 2 + states of various nuclei recoiling into vacuum or gas. The angular distributions are found to be perturbed by strong hyperfine fields generated by the highly ionized atoms. Both in vacuum and in gas, the interaction is found to be predominantly magnetic dipole and of a rapidly fluctuating character. In gas, the fluctuations in the field direction are due to collisions (at the rate of about 2 × 10 13 sec −1 at atmospheric pressure), and in vacuum they are brought about by optical transitions (at a rate of about 3 × 10 11 sec −1 ). The average hyperfine field of Nd or Sm emerging from a solid target with 10 MeV kinetic energy is found to be 25.5 ± 2.5 MG. Measurements of g -factors of 2 + excited states have been carried out, and the values of g -factors (relative to g( 152 Sm )) are reported for 150 Sm, 154 Sm, 148 Nd and 150 Nd.

Lifetime measurements of some rotational levels by a new recoil method (II)

Abstract Lifetime measurements of some rotational levels have been carried out by observing the decay of the excited nuclei along the recoil path following Coulomb excitation with back-scattered oxygen ions. Mean lives were determined for levels in 161 Dy, 171 Yb, 167 Er, 183 W and 190 Os. In 161 Dy, the parameter g R determined from the mean life g R = 0.14 ± 0.02, is somewhat larger than the value calculated in a pair correlation theory. The abrupt change predicted by this theory in the g R values from 161 Dy to 163 Dy is definitely established.

Energy loss of protons in rare earth oxides and reduced transition probabilities for 2+→0+ transitions in even rotational nuclei

Measurements of gamma yields from thick targets of rare earth oxides bombarded by protons were combined with lifetime measurements to determine reduced E2 transition probabilities in 2/sup +/ - 0/sup +/ rotational transitions. The rate of energy loss of the protons in the target was determined by a measurement of the absorption of the gamma in the target material at different proton energies yielding the mean penetration of the protons into the target. (auth)

A new measurement of the 7Be(p,γ)8B cross-section with an implanted 7Be target

Abstract The 7 Be(p, γ ) 8 B capture reaction is of major importance to the physics of the sun and the issues of the “solar neutrino puzzle”. We report here on a new determination of the absolute cross section of this reaction, using a novel method which overcomes some of the major experimental uncertainties of previous measurements. We utilize a 7 Be target implanted into a Cu substrate and a uniformly scanned particle beam larger than the target spot, eliminating issues of target homogeneity and backscattering loss of 8 B reaction products. The target was produced using a beam of 1.8·10 10 /s 7 Be nuclei extracted at ISOLDE (CERN) from a graphite target bombarded by 1 GeV protons in a two-step resonant laser ionization source. The 7 Be nuclei were directly implanted into a copper substrate to obtain a target of 2 mm diameter with a total of 3.10 15 atoms. The measurement of the 8 B production cross section was carried out at the Van de Graaff laboratory of the Weizmann Institute of Science. We obtain for the S factor of the reaction: S 17 ( E cm = 1.09 MeV) = 22.7(1.2) eV. barn and S 17 ( E cm = 1.29 MeV) = 23.8(1.5) eV. barn, somewhat higher than other recent measurements. The present results can serve as a benchmark for further measurements of this cross section.

Gyromagnetic ratios of the first excited 2+ states in even Os isotopes

Abstract Integral precession measurements are reported for the 2+ states in 188Os, 190Os and 192Os. The levels were Coulomb excited with high-energy oxygen ions, and gamma rays were observed in coincidence with backscattered ions. A suitable environment of low perturbation was provided by letting the excited nuclei recoil into copper. The measured g-factors are g( 188 Os ) = 0.270±0.018 , g( 190 Os ) = 0.323±0.044 , g(i192Os) = 0.337±0.045.

Hyperfine interactions in isolated ions

ConclusionIt has been demonstrated that the effect of a tilted multifoil array on an ensemble of nuclei approaches a regular precession in a field of magnitude p〈H〉 in the direction of the tilt axis. The magnitude of the precession can, under certain circumstances, be considerably larger than in a transient field, the only other method available today for measurements in the picosecond range. The technology of multifoil arrays has not been fully mastered to date, the immediate objective being the construction of arrays which keep their shape and spacings for many hours in a particle beam.

Precession measurements following coulomb excitation with oxygen ions

Abstract Gyromagnetic ratios were measured by a method described in an earlier publication for the 2+ rotational states in 178Hf, 180Hf, 186W and 186Os. Previous measurements on other osmium isotopes have been revised in the light of recent life time measurements. A general survey is presented for the g-factors in even hafnium, tungsten and osmium isotopes. A general treatment of angular distributions in ring counter geometry is given in an appendix to this contribution.

Hyperfine interactions of the 6.13 MeV, 3− state of 16O in ions of low charge state

Abstract The hyperfine interactions of the 6.13 MeV, 3 − state of 16 O in ions recoiling into vacuum with velocity v / c = 1.06% have been studied using perturbed angular correlations. Time-differential and external magnetic field de-coupling experiments have been carried out. The de-coupling curve and the time dependence of the perturbation have been interpreted in terms of a microscopic calculation yielding values of ¦g¦ = 0.57 ± 0.05 and 0.54 ± 0.05 respectively, for the g -factor of the 3 − state. A value of 26.6 ± 0.7 ps for the lifetime of this level was also obtained as a by-product of the investigation.