Experimental study of theβ-delayed neutron decay ofN21

Abstract

The first spectroscopic study for the β decay of N21 is carried out based on β–n, β–γ, and β–n–γ coincidence measurements. The neutron-rich N21 nuclei are produced by the fragmentation of the E/A=68.8 MeV Mg26 primary beam on a thick Be9 target and are implanted into a thin plastic scintillator that also plays the role of β detector. The time of flight of the emitted neutrons following the β decay are measured by the surrounding neutron sphere and neutron wall arrays. In addition, four clover germanium detectors are used to detect the β-delayed γ rays. Thirteen new β-delayed neutron groups are observed with a total branching ratio of 90.5±4.2%. The half-life for the β decay of N21 is determined to be 82.9±7.5 ms. The level scheme of O21 is deduced up to about 9 MeV excitation energy. The experimental results for the β decay of N21 are compared to the shell-model calculations.5 MoreReceived 22 December 2008DOI:https://doi.org/10.1103/PhysRevC.80.054315©2009 American Physical Society