POSITRON DECAYS OF TI-42 AND CA-38

The positron decay of Ti42 has been investigated using the Ca40(h,n) reaction with a natural calcium target. A strong 610.7±0.5-keV ray with a half-life T12=0.202±0.005 sec is attributed to a positron branch to the 611-keV level of Sc42. A weak 2222±2-keV ray has been observed, which corresponds to a positron branch to the 2223-keV level of Sc42. Using this measured half-life and the decay energies, the branching ratios are calculated from decay systematics to be r0+=(44.1±1.2)%, r1+=(55.2±1.2)%, and r9+=(0.7±0.3)%. The logft values 3.179±0.015 and 4.36-0.24+0.16 establish J=1+ for both the 611- and the 2223-keV states of Sc42. The positron decay of Ca38 has been investigated using the Ar36(h,n) reaction. The half-life 0.439±0.012 sec has been measured for this decay. In addition to the strong Gamow-Teller transition feeding the 1695-keV level of K38, a weak 3210±2-keV -ray line has been observed which is tentatively attributed to a transition from the 3337-keV level in K38 fed by a (0.6±0.2)% + branch of Ca38. Its logft (3.90-0.13+0.10) then establishes the J=1+ assignment for this state. © 1969 The American Physical Society.