States in 22O via β decay of 22N

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