• Sabina Sahadevan

      Articles written in Pramana – Journal of Physics

    • Cold valleys in the radioactive decay of 248-254Cf isotopes

      R K Biju Sabina Sahadevan K P Santosh Antony Joseph

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      Based on the concept of cold valley in cold fission and fusion, we have investigated the cluster decay process in 248-254Cf isotopes. In addition to alpha particle minima, other deep minima occur for S, Ar and Ca clusters. It is found that inclusion of proximity potential does not change the position of minima but minima become deeper. Taking Coulomb and proximity potential as interacting barrier for post-scission region, we computed half-lives and other characteristics for various clusters from these parents. Our study reveals that these parents are stable against light clusters and unstable against heavy clusters. Computed half-lives for alpha decay agree with experimental values within two orders of magnitude. The most probable clusters from these parents are predicted to be 46Ar, 48,50Ca which indicate the role of doubly or near doubly magic clusters in cluster radioactivity. Odd A clusters are found to be favorable for emission from odd A parents. Cluster decay model is extended to symmetric region and it is found that symmetric fission is also probable which stresses the role of doubly or near doubly magic 132Sn nuclei. Geiger-Nuttal plots were studied for various clusters and are found to be linear with varying slopes and intercepts.

    • Stability of 244-260Fm isotopes against alpha and cluster radioactivity

      K P Santhosh R K Biju Sabina Sahadevan

      More Details Abstract Fulltext PDF

      Taking Coulomb and proximity potentials as the interacting barrier we have studied the cold valley in the radioactive decay of 244-260Fm isotopes. It is found that in addition to alpha particle minima, other minima occur at S, Ar and Ca clusters. We have computed the half-lives and other characteristics of different clusters emitted from these parents treating parent, daughter and emitted cluster as spheres. Our study reveals that most of these parents are unstable against alpha and heavy cluster (46Ar, 48,50Ca) emissions and stable against light cluster emission, except 8Be from 244-248Fm isotopes. The most probable clusters from these parents are predicted to be 46Ar, 48,50Ca which indicate the role of doubly or near doubly magic clusters ($Z = 20$, $N = 28$) and also stress the role of doubly magic 208Pb daughter. The computed half-lives for alpha decay are in good agreement with the experimental data. It is found that the presence of neutron excess in the parent nuclei slows down the cluster decay process. The effect of quadrupole $(\beta_{2})$ and hexadecapole $(\beta_{4})$ deformations of parent and fragments on half-lives are also studied. It is found that inclusion of $\beta_{2}$ and $\beta_{4}$ reduces the height and shape of the barrier (increases barrier penetrability) and hence the half-life decreases.

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