SEARCH FOR CLUSTER RADIOACTIVITY OF NP-237

The few odd-A nuclides known to exhibit cluster radioactivity decay at rates hindered with respect to their even-even neighbors. For Np-237, the most likely clusters are predicted to be Mg-30 and Si-32. We have completed a rigorous search for cluster emission from Np-237, with a null result. Our 90% confidence limit on the branching ratio with respect to alpha emission, B (cluster/alpha) < 1.8 x 10(-14), is a factor 4.3 lower than the limit obtained by Tretyakova et al. The two experiments together place an upper limit of 1.5 x 10(-14) on the branching ratio for emission of clusters with 10 less-than-or-equal-to Z less-than-or-equal-to 14 from Np-237.