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Low-Intensity Branches in the Ti 45 Decay

1966; American Institute of Physics; Volume: 146; Issue: 3 Linguagem: Inglês

10.1103/physrev.146.774

1536-6065

F. T. Porter, M. S. Freedman, F. Wágner, K.A. Orlandini,

Muon and positron interactions and applications

The decay of ${\mathrm{Ti}}^{45}$ (\ensuremath{\sim}100% electron capture and ${\ensuremath{\beta}}^{+}$ to the ${\mathrm{Sc}}^{45}$ ground state) has been reinvestigated with the Argonne toroidal-field beta spectrometers and with lithium-drifted germanium gamma detectors. New low-intensity branches to levels in ${\mathrm{Sc}}^{45}$ at 725.1\ifmmode\pm\else\textpm\fi{}0.8 [149\ifmmode\pm\else\textpm\fi{}35], 1238\ifmmode\pm\else\textpm\fi{}1.5 [16\ifmmode\pm\else\textpm\fi{}6], and 1411.3\ifmmode\pm\else\textpm\fi{}0.9 [112\ifmmode\pm\else\textpm\fi{}30] keV have been found. Numbers in brackets are the intensities for ${10}^{5}$ decays. The 12.4-keV level in ${\mathrm{Sc}}^{45}$ previously seen in the $\ensuremath{\beta}$ decay of ${\mathrm{Ca}}^{45}$ is also populated in the ${\mathrm{Ti}}^{45}$ decay; its energy is ${12.40}_{\ensuremath{-}0.01}^{+0.02}$ keV and its intensity is [12\ifmmode\pm\else\textpm\fi{}3]. The intensity of the first-forbidden unique decay ($\frac{7}{2}\ensuremath{-}$ to $\frac{3}{2}+$) to the 12.4-keV state is not known because of the unknown amount of gamma branching to the 12.4-keV state from higher levels in ${\mathrm{Sc}}^{45}$, but from the observed 12.4-keV intensity, $log{f}_{1}t>8.1$. No evidence was found for beta decay to the 376-keV level [60] or to the 540-keV level [9]. $\mathrm{Log}\mathrm{ft}$ values for beta decays to the three states at 725, 1238, and 1411 keV are 6.3, 6.8 and 5.6, respectively. In general, to the other states, $log\mathrm{ft}$ values are greater than 7, with the exception of the 1660-keV state for which our gamma intensity limit yields $log\mathrm{ft}5.7$. The available data are consistent with spin and parity assignments of (${\frac{3}{2}}^{+}$) for the 12.4-keV state and (${\frac{3}{2}}^{\ensuremath{-}}$) for the 376-keV state. The end point of the positron spectrum, 1044\ifmmode\pm\else\textpm\fi{}5 keV, indicates a total decay energy, ${\mathrm{Ti}}^{45}$ \ensuremath{\rightarrow} ${\mathrm{Sc}}^{45}$, of 2066\ifmmode\pm\else\textpm\fi{}5 keV, 20 to 40 keV higher than earlier measurements and in better agreement with reaction data, 2062\ifmmode\pm\else\textpm\fi{}4 keV. Our half-life measurement of 3.08\ifmmode\pm\else\textpm\fi{}0.01 h agrees with previous measurements.