Identification of four new neutron-rich rare-earth isotopes

Four new neutron-rich fission-product nuclei were identified at the on-line mass separator TRISTAN at Brookhaven National Laboratory. These nuclei are of particular significance in astrophysical nucleosynthesis calculations, since they lie in the region of the rare-earth maximum in r-process abundances. Their half-lives were measured to be T1/2 = 28.2 + or - 1.1 sec for Pm-156, T1/2 = 15 + or - 2 sec for Sm-159, T1/2 = 8.7 + or - 1.4 sec for Sm-160, and T1/2 = 27 + or - 3 sec for Eu-161. It is noted that a comparison of these and other new half-lives with recent calculations reveals a characteristic pattern of discrepancies.