The low-energy part of the radiation emitted after thermal neutron capture in ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ has been investigated by different experimental techniques: Gamma-ray measurements were performed with a diffraction spectrometer. The conversion electron spectrum was recorded with a $\beta$ spectrograph and measurements of gamma-gamma coincidences were carried out. For ten rotational bands in ${}_{}{}^{182}{}_{}{}^{}\mathrm{Ta}$, which were already proposed in an earlier work, a large amount of new decay data has been obtained and for most of these bands higher rotational levels have been found. These ten bands have for their lowest level the following energies and $I^{\pi }K$ values: 0 keV $3^{-}$3, 16 keV $5^{+}$5, 114 keV $4^{-}$4, 150 keV $4^{+}$4, 173 keV $5^{-}$5, 250 keV $3^{+}$3, 270 keV $2^{-}$2, 402 keV $2^{+}$2, 547 keV $3^{-}$3, and 558 keV $1^{-}$0. New rotational bands with the following band head energies and structure have been established: 443.6 keV ${\{\frac{5}{2^{+}}{\mathrm{}\left[402\right]\mathrm{}}_p, \frac{3}{2^{-}}{\mathrm{}\left[512\right]\mathrm{}}_n\}}_{K=1\mathrm{}}$, 593.0 keV ${\{\frac{7}{2^{+}}{\mathrm{}\left[404\right]\mathrm{}}_p, \frac{9}{2^{+}}{\mathrm{}\left[624\right]\mathrm{}}_n\}}_{K=1\mathrm{}}$, and 647.6 keV ${\{\frac{5}{2^{+}}{\mathrm{}\left[402\right]\mathrm{}}_p, \frac{1}{2^{-}}{\mathrm{}\left[510\right]\mathrm{}}_n\}}_{K=2\mathrm{}}$. Tentative band heads have been proposed at 390, 740, and 749 keV with $I^{\pi }K$ values $6^{+}$6, $2^{-}$2, and $3^{+}$3. For the sake of completeness, previously found levels with $K$ values ranging from seven to ten are also discussed.

NUCLEAR REACTIONS ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$($n$,$\gamma$), $E=\mathrm{thermal}$; measured $E_{\gamma }$, $I_{\gamma }$, $I_{\mathrm{ce}}$, $\gamma \gamma$ co-incidences. ${}_{}{}^{182}{}_{}{}^{}\mathrm{Ta}$ deduced levels $J$, $\pi$, $K$, $\mathrm{cc}$, $\gamma$ multipolarities, $J$ of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ neutron resonances. Natural targets.

• Received 19 December 1978

DOI:https://doi.org/10.1103/PhysRevC.20.504