Enhanced <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi></mml:math> decays to negative-parity states in even-even nuclei with octupole deformation
W. M. Seif, A. Adel, N. V. Antonenko, G. G. Adamian
Abstract
The $\ensuremath{\alpha}$ decays of even-even Ra, Th, U, and Pu isotopes to ground and excited states of daughter nuclei with neutron numbers of $N=130--140$ are investigated. These nuclei show some enhanced $\ensuremath{\alpha}$-branching ratios to negative-parity states $({1}^{\ensuremath{-}},$ ${3}^{\ensuremath{-}})$, compared with the decays to positive-parity states $({4}^{+})$ of comparable energy. This enhancement correlates with appearance of static octupole deformation, rather than spherical nuclear shapes or dynamic asymmetric vibrational states. The highly enhanced branching ratios occur for $\ensuremath{\alpha}$ decays to the ${1}^{\ensuremath{-}}$ and ${3}^{\ensuremath{-}}$ states of the Ra isotopes with $N=134, 136, 138$, then to ${1}^{\ensuremath{-}}$ state in Th $(N=134--140)$ and to the ${3}^{\ensuremath{-}}$ state in Rn $(N=132--136)$ isotopes.