Yu-Cheng Ge

Observation of a new transition in the {beta}-delayed neutron decay of {sup 18}N

A new transition is reported in the beta-delayed neutron decay of {sup 18}N. The observed neutron energy is 3.78{+-}0.05 MeV with a branching ratio of 0.05{+-}0.03%, which corresponds to an excitation energy of 12.05{+-}0.05 MeV in the daughter nucleus {sup 18}O. The log ft value of this transition is 5.24{+-}0.3, which, together with the previously reported electron scattering data, determines the J{sup {pi}} value of this level to be 1{sup -}. The experimental data are compared to the shell model calculations in different model spaces.

Experimental study of the {beta}-delayed neutron decay of {sup 21}N

The first spectroscopic study for the beta decay of N-21 is carried out based on beta-n, beta-gamma, and beta-n-gamma coincidence measurements. The neutron-rich N-21 nuclei are produced by the fragmentation of the E/A=68.8 MeV Mg-26 primary beam on a thick Be-9 target and are implanted into a thin plastic scintillator that also plays the role of beta detector. The time of flight of the emitted neutrons following the beta decay are measured by the surrounding neutron sphere and neutron wall arrays. In addition, four clover germanium detectors are used to detect the beta-delayed gamma rays. Thirteen new beta-delayed neutron groups are observed with a total branching ratio of 90.5 +/- 4.2%. The half-life for the beta decay of N-21 is determined to be 82.9 +/- 7.5 ms. The level scheme of O-21 is deduced up to about 9 MeV excitation energy. The experimental results for the beta decay of N-21 are compared to the shell-model calculations.