NEUTRON-DEFICIENT MEMBERS OF A=139 DECAY CHAIN .1. 5.5-H ND-139M AND 30-MIN ND-139G

We have studied the γ rays emitted following the decays of 5.5-h Nd139m and 30-min Nd139g with Ge (Li) and NaI (T1) detectors in singles, coincidence, and anticoincidence configurations. Our study has indicated 51 γ rays accompanying Nd139m decay and 21 that follow Nd139g decay. Of these, 56 have been placed in decay schemes containing a total of 22 excited states. The decay scheme of 32+Nd139g has much in parallel with those of similar nuclei in this region, and states are populated in Pr139 at 0(52+), 113.8 (72+), 405.0 (32+,12+), 589.2 (52+), 916.8(12+,32+), 1074.4 (12+,32+), 1311.8(12+,32+,52+), 1328.2 (52+), 1405.5 (12+,32+,52+), 1449.5 (12+,32+,52+), and 1501.2keV(12+,32+). On the other hand, 11/2- Nd139m decays only 12.7% via a 231.2-keV M4 isomeric transition and independently decays by electron capture to a set of almost completely different states in Pr139. These are at 0 (52+), 113.8(72+), 821.9(112-), 828.1(72+,92+), 851.9(92+,72+), 1024.0(72+,92+,112+), 1396.6(92,112,132), 1523.2,1624.5(92-,112-), 1834.1(92-,112-), 1927.1(92-,112-), 2048.8(92-,112-), 2174.3(92-,112-), and 2196.7keV(92-,112-). Some 80.7% of its decay goes to the last six states, and we interpret them as being three-quasiparticle states. It appears that Nd139m is one of a few nuclides whose intrinsic structure forces the preferred mode of decay to go into a three-quasiparticle multiplet, i.e., (πd52)2(νd32)-2(νh112)-1→(πd52)(νd32)-1(νh112)-1. The three-quasiparticle states are depopulated by numerous enhanced γ transitions between states in the multiplet and fewer, apparently highly hindered, transitions to lower states. Thus, the potential exists for extracting information about states near 2 MeV in this nucleus that normally is available only for states near the ground state. © 1969 The American Physical Society.