Relative longevity of odd-N nuclei in the heavy actinide region

Abstract

It is shown that, contrary to the normal feature witnessed all across the periodic table that even–even nuclei are more abundant/longer-lived than their odd-A neighbours, many odd-mass heavy nuclei are seen to be much longer-lived than their even–even neighbours. In the trans-plutonium domain of even-Z actinides, all the predominantly alpha-decaying odd-N nuclei are longer-lived than their even-mass neighbours. Similar behaviour is observed for heavy odd-Z actinides as well. A semi-empirical criterion is stated to determine the relative longevity of the odd-N and even-N nuclei. This feature is sought to be explained by examining the respective alpha decay rates. A detailed discussion of α-decays of the β-stable curium (Z = 96) isotopic chain is presented to illustrate this phenomenon. Correspondence with a similar occurrence in spontaneously fissioning nuclei is briefly pointed out.