Landau-Zener effect in cluster decay

Abstract

The influence of the Landau-Zener effect on the fine structure of the cluster decay phenomenon is evidenced. Estimations of hindrance factors are reported for the 14 C emission from 223 Ra. The half-lives are calculated considering the cluster decay as a superasymmetric fission process appealing to the Wentzel-Kramers-Brillouin penetrabilities. The excitation of the last unpaired nucleon is considered to be due mainly to the Landau-Zener promotion mechanism. The deformation energy is computed in the framework Yukawa-plus-exponential model extended for binary systems with different charge densities and adding the specialization energy of the unpaired nucleon. The Werner-Wheeler approximation is used to compute the effective mass. Assuming molecular states during the disintegration, the superasymmetric two-center shell model is used to obtain the level scheme of the cluster decay. ͓S0556-2813͑98͒06205-0͔

Intrinsic energy partition in fission

“…These energies are calculated within the Woods-Saxon two center model and the internuclear is considered to be 10 6 m/s. This velocity gives a tunneling time of 10 −21 s. A similar value resorts in calculations devoted to alpha [25] and cluster decays [26][27][28]. This internuclear velocity is in agreement with the results obtained in Ref.…”

Landau-Zener effect in fission

“…The realistic two-center diagram presented before provides an instrument to study the role of individual orbitals during the disintegration process in a similar way as the study of nucleus-nucleus collisions [22,23] or the alpha-and cluster-decays [24,25]. Levels with same quantum numbers associated to some symmetries of the system cannot cross during the disintegration process and exhibit avoided level crossing.…”

Fine structure ofαdecay in odd nuclei

“…Recently, a theory based on the Landau-Zener effect was developed [5][6][7] intending to describe quantitatively the cluster decay fine structure phenomenon. This new formalism succeeds to reproduce the values of the fine structure hindrance factors for the 14 C emission from 223 Ra being in a better agreement than other microscopic theories [8] with the experiment.…”

“…[9] and improved in Ref. [5] was modified in order to reproduce the single-particle levels assumed to describe an α cluster in the final stage of the disintegration. Consequently, the alpha oscillator stiffnesshω 2α was forced to vary gradually from the usual STCSM valuehω 2 = 41A 1/3 2 when the normalized coordinate R n =0, to the value extracted from Ref.…”