Decay Scheme of the Mirror NucleusP29and Related Results

Abstract

The decay of ${\mathrm{P}}^{29}$ has been investigated with scintillation spectrometers, single and in coincidence. Positron emission (3.945±0.005 Mev end-point energy for the most energetic spectrum) occurs with a half-life of 4.45±0.05 sec to the ground state and to excited levels of ${\mathrm{Si}}^{29}$ at 1.28, 2.43, and possibly 2.03 Mev. Branching ratios (in percent) of 98.8±0.4 (ground state), 0.8±0.2 (1.28-Mev level), <0.15 (2.03-Mev level), and ${0.24}_{-0.08\mathrm{}}^{+0.26\mathrm{}}$ (2.43-Mev level) were measured. A study of $\gamma$ rays from the decay of ${\mathrm{Al}}^{29}$ to ${\mathrm{Si}}^{29}$ led to branching ratios (in percent) of 15±9 (1.28-Mev level), <4 (2.03-Mev level), and 85±9 (2.43-Mev level). The intensity of a 1.15-Mev $\gamma$ ray (cascading from the 2.43-Mev level) has been set at <11 percent of the total ${\mathrm{Al}}^{29}$ decays. Spin and parity assignments of the ${\mathrm{Si}}^{29}$ levels are discussed and compared with the results of other experiments. The $\mathrm{ft}$ values of the ${\mathrm{P}}^{29}$ decay are shown to agree with values calculated from the coupling constants of $\beta$ decay if the theories of Feenberg and Bohr are used.