States In O-22 Via Beta Decay Of N-22

The energy-level structure of O-22 with the recently identified N = 14 subshell closure was investigated by the beta decay of N-22 for the first time. A beta-delayed-neutron, time-of-flight measurement revealed six new neutron transitions attributed to the beta decay of N-22. One-and two-beta-delayed neutron decay of N-22, with emission probabilities of 33(3)% and 12(3)%, respectively, were observed to correspond to four new negative-parity states in O-22. The half-life of N-22 beta decay was determined to be 20(2) ms. Three gamma-ray transitions in O-22 and single gamma rays in O-21 and O-20 were observed following the beta decay of N-22. The observation of large Gamow-Teller strength for a highly excited state in O-22 indicates a halo structure for N-22. A comparison of results with shell-model predictions showed overall poor agreement. The measured P-n values of O-24 and F-25 components of the secondary beam showed an enhancement relative to the P-n values of adjacent oxygen and fluorine isotopes, providing additional evidence for the N = 14 closed subshell.