We measured the β-delayed α-particle emission spectrum of ${}^{16}\mathrm{N}$ with a sensitivity for β-decay branching ratios of the order of ${10}^{-10}$. The ${}^{16}\mathrm{N}$ nuclei were produced using the $d($${}^{15}\mathrm{N}$,${}^{16}\mathrm{N}$)$p$ reaction with 70 MeV ${}^{15}\mathrm{N}$ beams and a deuterium gas target 7.5 cm long at a pressure of 1250 torr. The ${}^{16}\mathrm{N}$ nuclei were collected (over 10 s) using a thin aluminum foil with an areal density of 180 μg/cm${}^2$ tilted at $7^{°}$ with respect to the beam. The activity was transferred to the counting area by means of a stepping motor in less than $3s$ with the counting carried out over $8s$. The β-delayed α-particles were measured using a time-of-flight method to achieve a sufficiently low background. Standard calibration sources (${}^{148}\mathrm{Gd}$, ${}^{241}\mathrm{Am}$, ${}^{208,209}\mathrm{Po}$, and ${}^{227}\mathrm{Ac}$) as well as α particles and ${}^7\mathrm{Li}$ from the ${}^{10}\mathrm{B}$$(n,\alpha )$${}^7\mathrm{Li}$ reaction were used for an accurate energy calibration. The energy resolution of the catcher foil (180–220 keV) was calculated and the time-of-flight resolution (3–10 nsec) was measured using the β-delayed α-particle emission from ${}^8\mathrm{Li}$ that was produced using the $d($${}^7\mathrm{Li}$,${}^8\mathrm{Li}$)$p$ reaction with the same setup. The line shape was corrected to account for the variation in the energy and time resolution and a high statistics spectrum of the β-delayed α-particle emission of ${}^{16}\mathrm{N}$ is reported. However, our data (as well as earlier Mainz data and unpublished Seattle data) do not agree with an earlier measurement of the β-delayed α-particle emission of ${}^{16}\mathrm{N}$ taken at TRIUMF after averaging over the energy resolution of our collection system. This disagreement, among other issues, prohibits accurate inclusion of the f-wave component in the R-matrix analysis.

• Received 7 February 2007

DOI:https://doi.org/10.1103/PhysRevC.75.065802