RESUMO
Excited states of the neutron-rich nuclei (97,99)Rb were populated for the first time using the multistep Coulomb excitation of radioactive beams. Comparisons of the results with particle-rotor model calculations provide clear identification for the ground-state rotational band of (97)Rb as being built on the πg(9/2) [431] 3/2(+) Nilsson-model configuration. The ground-state excitation spectra of the Rb isotopes show a marked distinction between single-particle-like structures below N=60 and rotational bands above. The present study defines the limits of the deformed region around Aâ¼100 and indicates that the deformation of (97)Rb is essentially the same as that observed well inside the deformed region. It further highlights the power of the Coulomb-excitation technique for obtaining spectroscopic information far from stability. The (99)Rb case demonstrates the challenges of studies with very short-lived postaccelerated radioactive beams.
RESUMO
Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.
RESUMO
A ß-decaying high-spin isomer in (96)Cd, with a half-life T(1/2)=0.29(-0.10)(+0.11) s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of (124)Xe on a (9)Be target. From the half-life and the observed γ decays in the daughter nucleus, (96)Ag, we conclude that the ß-decaying state is the long predicted 16(+) "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πν(p(1/2),g(9/2)) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N=Z=50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the πν(g,d,s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer.
RESUMO
The value of serum beta-carotene concentration as an indicator of steatorrhoea was investigated in 50 patients with steatorrhoea (fecal fat greater than 7 g/day), 53 controls, and 22 patients with gastrointestinal disease without steatorrhoea. In the control group, beta-carotene concentrations were normally distributed when plotted logarithmically. The mean value was 131 micrograms/dl. The lower limit of normal, based on a 2-SD confidence interval, was 47 micrograms/dl. beta-Carotene concentrations and fecal fat excretion were correlated in a reciprocal, hyperbolic function (r = -0.66). Twenty-nine of the 50 patients with steatorrhoea had beta-carotene concentrations less than 47 micrograms/dl (sensitivity 58%; specificity 93%). Referring to an additional cut-off point of 100 micrograms/dl, beta-carotene concentration had a sensitivity of 88%. These data show that low plasma beta-carotene concentrations (less than 47 micrograms/dl) can be regarded a specific and useful indicator of steatorrhoea and thus obviate fecal fat analysis. Values greater than 47 micrograms/dl, however do not exclude steatorrhoea. Based on a two-step interpretation beta-carotene is thus both a useful screening test for steatorrhoea (with a cut-off point of 100 micrograms/dl) and, more important, a valid, simple, and clinically practical alternative for fecal fat analysis (if values are less than 47 micrograms/dl).
