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The ␤ decay of 11 Li has been investigated at TRIUMF-ISAC using a high-efficiency array of Compton suppressed HPGe detectors. From a line-shape analysis of the Doppler-broadened peaks observed in the 10 Be ␥ spectrum, both the half-lives of states in 10 Be and the energies of the ␤-delayed neutrons feeding those states were obtained. Furthermore, it was possible to determine the excitation energies of the parent states in 11 Be with uncertainties comparable to those obtained from neutron spectroscopy experiments. These data suggest that the ␤ decay to the 8.81 MeV state in 11 Be occurs in the 9 Li core and that one neutron comprising the halo of 11 Li survives in a halolike configuration after the ␤-delayed neutron emission from this level.

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The TRIUMF-ISAC gamma-ray escape-suppressed spectrometer (TIGRESS) is a new γ -ray detector array being developed for use at TRIUMF's Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. TIGRESS will comprise 12 32-fold segmented clover-type HPGe detectors coupled with 20-fold segmented modular Compton suppression shields and custom digital signal processing electronics. This paper provides an overview of the TIGRESS project and progress in its development to date.

High-precision measurements of the half-life and β-branching ratios for the β − decay of 26 Na to 26 Mg have been measured in β-counting and γ -decay experiments, respectively. A 4π proportional counter and fast tape transport system were employed for the half-life measurement, whereas the γ rays emitted by the daughter nucleus 26 Mg were detected with the 8π γ-ray spectrometer, both located at TRIUMF's isotope separator and accelerator radioactive beam facility. The half-life of 26 Na was determined to be T 1/2 = 1.07128 ± 0.00013 ± 0.00021 s, where the first error is statistical and the second systematic. The logf t values derived from these experiments are compared with theoretical values from a full sd-shell model calculation.