New Delayed-Neutron-Emitting Isotope:Be12

Delayed neutrons with a half-life of 11.4±0.5 msec have been observed in the GeV-energy proton irradiation of targets of ${\mathrm{N}}^{15}$ and heavier nuclei but not from ${\mathrm{N}}^{14}$ and lighter nuclei. This new activity has been assigned to ${\mathrm{Be}}^{12}$. Cross sections for production of this nuclide from ${\mathrm{N}}^{15}$, ${\mathrm{O}}^{16}$, ${\mathrm{O}}^{18}$, F, Na, and Al have been measured. From cross-section systematics, it is estimated that delayed neutrons are emitted in about 7% of the decays. Upper limits for the delayed-neutron branches of ${\mathrm{He}}^8$ and ${\mathrm{B}}^{13}$ have been set at 3 and 0.3%, respectively.