No abstract

There is strong circumstantial evidence that the shape of atomic nuclei with particular values of Z and N prefers to assume octupole deformation, in which the nucleus is distorted into a pear shape that loses the reflection symmetry of a quadrupole-deformed (rugby ball) shape prevalent in nuclei. Recently, useable intensities of accelerated beams of heavy, radioactive ions have become available at the REX-ISOLDE facility at CERN. This has allowed electric octupole transition strengths, a direct measure of octupole correlations, to be determined for short-lived isotopes of radon and radium expected to be unstable to pear-like distortions. The data are used to discriminate differing theoretical approaches to the description of the octupole phenomena, and also help restrict the choice of candidates for studies of atomic electric-dipole moments, that provide stringent tests of extensions to the Standard Model.

No abstract

The production of the 26 Al radioisotope in astrophysical environments is not understood, in part, because of large uncertainties in key nuclear reaction rates. The 25 Al(p,␥) 26 Si reaction is one of the most important, but its rate is very uncertain as a result of the lack of information on the 26 Si level structure above the proton threshold. To reduce these uncertainties, we have measured differential cross sections for the 28 Si(p,t) 26 Si reaction and determined excitation energies for states in 26 Si. A total of 21 states in 26 Si were observed, including ten above the proton threshold. One new state at 7019 keV was observed, the excitation energies of several states were corrected, and the uncertainties in the excitation energies of other states were significantly reduced. Spins and parities of several states above the proton threshold were determined for the first time through a distorted-wave Born approximation analysis of the angular distributions. These results substantially clarify the level structure of 26 Si.