Abstract
An iron-free intermediate-image spectrometer has been used to measure the beta-ray spectra of 2.25-sec , 7.4-sec , and 29-sec and to measure the positron-electron internal pair conversion lines occurring in and decays. emits a beta-ray branch of end-point energy 9.82±0.04 Mev to the ½- ground state of and a branch of 4.51±0.03-Mev end-point energy. Relative intensities are (32±2)% () and 68% (), respectively, and both components have the allowed shape. From pair line measurements at 1.5% resolution the gammaray energy is 5.299±0.006 Mev, and thus the inner beta-ray group leads to the upper member of the (5.276-5.305)-Mev doublet level in known from the reaction. The internal pair conversion coefficient derived for the 5.299-Mev line agrees best with an assignment. Our data require spin and parity ½+ or for the 5.305-Mev level in , and spin and parity ½+ or for . Taken together with other evidence it seems likely that both states are ½+. No evidence could be found from gamma-ray measurements for the beta decay of to other known states of . Some comments are made on the intermediate-coupling model for . In the decay of we find that the 3.3-Mev beta-ray branch to the 7.11-Mev level in is <11% per decay, based on the Kurie-plot analysis. A value of (4.7±0.9)% per decay for this branch is derived from the intensity of the 7.11-Mev pair line. decays with beta-ray branches of 4.601±0.015 Mev [()%, ] and 3.25±0.02 Mev (58.5%, ). Other results include a value of 5.416±0.015 Mev for the beta-ray end-point energy of and a value of 6.051±0.005 Mev for the energy of the pair-emitting state of .
- Received 16 June 1959
DOI:https://doi.org/10.1103/PhysRev.116.939
©1959 American Physical Society