Weak Branchings in the Decay of P34, Cl34, and P30

Abstract

The gamma rays following the beta decays of ${\mathrm{P}}^{34}$, ${\mathrm{Cl}}^{34}$, and ${\mathrm{P}}^{30}$ were investigated with a NaI scintillation spectrometer and a twenty-channel analyzer. An unsuccessful search was made for a gamma ray with an energy of 3.22 Mev from ${\mathrm{P}}^{34}$ which should result from an allowed beta-decay branching to the second excited state in ${\mathrm{S}}^{34}$. Since no such gamma ray was found, this branching, if it exists, is very weak, with a $log\mathrm{ft}$ value higher than 5.6. Together with the known branching to the first excited state and the transition rates from the ${\mathrm{Cl}}^{34}$ $3^{+}$ isomeric state, the above result suggests that the second excited state in ${\mathrm{S}}^{34}$ has a configuration similar to that of the ${\mathrm{Cl}}^{34}$ isomeric state and that the first excited state resembles the ${\mathrm{P}}^{34}$ ground state. For explaining the transition rate to the ground state from ${\mathrm{P}}^{34}$, the assumption of strong mixing of both types in the ${\mathrm{S}}^{34}$ ground state seems to be necessary. This strong mixing in the $0^{+}$ ground state also gives an explanation for the inversion of the order of the lowest $T=0\mathrm{}$ and $T=1\mathrm{}$ states of ${\mathrm{Cl}}^{34}$. An additional state of ${\mathrm{S}}^{34}$ at 4 Mev, which is attained from both the ${\mathrm{P}}^{34}$ and the ${\mathrm{Cl}}^{34}$ $3^{+}$ state and is thus to be interpreted as a $2^{+}$ state, was found. In the case of ${\mathrm{P}}^{30}$ a beta-decay branching to the first excited state of ${\mathrm{Si}}^{30}$ was looked for. A weak gamma ray of 2.24 Mev was found, indicating a branching of 0.2% with a $log\mathrm{ft}$ of 5.4.