No abstract

When highly enriched samples of Sm 152 and Sm 154 are irradiated with 14.8-Mev neutrons, activities having half-lives of 6.5±0.5 min and 2.5±0.5 min are observed. On the basis of yields and cross-bombardments, these are assigned to new isotopes Pm 152 and Pm 154 , respectively. Cross-section measurements at 14.8 Mev for (n,2n), (n,p), and (n,a) reactions of samarium are reported, the experimental values being as follows: Sm 144 (rc», 1200=b300 mb; Sm 154 (ra», 1500±300 mb; Sm™(n } p), 3.7±0.2 mb; Sm™(n,p), 3.5±0.2 mb; Sm 152 (w,a), 10d=2 mb; and Sm 154 (»,a), 9±3 mb. While the (n,2n) cross sections are within an order-ofmagnitude agreement with statistical evaporation theory, the experimental values for the (n,p) and (n,a) cross sections are several orders of magnitude larger than those calculated from statistical evaporation theory based on the compound nucleus model.