#### Abstract

The extent of particle-photon mixing in ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$ and ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ has been determined using the ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d,t)$ and ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d,{d}^{\prime})$ reactions. ${K}^{\pi}={2}^{-}$ bands were identified at 593 and 1477 keV in ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$. Since the only ${K}^{\pi}={2}^{-}$ neutron two quasiparticle configuration expected below 2 MeV in ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$ is ${\left\{{\frac{9}{2}}^{-}\mathrm{}\right[734];{\frac{5}{2}}^{+}\mathrm{}[622\left]\right\}}_{2-}$, the second ${K}^{\pi}={2}^{-}$ band is considered to be predominantly of phonon character. In ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ a ${K}^{\pi}={\frac{5}{2}}^{+}$ band at 145 keV, known from decay scheme studies, receives a measurable population in the ($d,{d}^{\prime}$) reaction. The phonon admixture in the ${\frac{5}{2}}^{+}$ state which results from the $\left\{{\frac{9}{2}}^{-}\mathrm{}\right[734]\mathrm{}\otimes {2}^{-}\mathrm{phonon}\}$ configuration was determined to be (29±5)%. The collective admixture in the ${\frac{5}{2}}^{+}$ state was also calculated from an octupole particle-hole interaction and was found to be 35%, in good agreement with the experimental value. The anomalously low energy of the ${\frac{5}{2}}^{+}$ state could not be entirely reproduced by this calculation.

NUCLEAR REACTIONS ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d,{d}^{\prime})$, ${E}_{d}=15\mathrm{}$ MeV; ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}(d,t)$, ${E}_{d}=12\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$. ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cf}$, ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ deduced levels, $J$, $\pi $, extracted phonon contributions. Enriched target. Calculated particle-phonon mixing.

DOI: http://dx.doi.org/10.1103/PhysRevC.12.442

- Received 14 May 1975
- Published in the issue dated August 1975

© 1975 The American Physical Society