Evidence for a Nuclear Tensor Force from Mass-14 Beta- and Gamma-Ray Data

The role of beta- and gamma-ray matrix elements in the determination of wave functions for the $s^4{p}^{10}$ states of mass 14 is examined. The data considered include the Gamow-Teller (beta) matrix elements of ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ and the $M1\mathrm{}$ and $E2\mathrm{}$ matrix elements connecting the lowest four $s^4{p}^{10}$ states of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$. The magnetic moment of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ is also discussed. The shell-model wave functions considered arise mainly from the $s^4{p}^{10}$ configuration but include admixtures of the $s^4{p}^8$ ($2s, 1d$) configuration. It is found that the data, considered as a whole, cannot be explained if the $s^4{p}^{10}$ components of the wave functions are derived from a central plus spin-orbit interaction only, but that quite satisfactory agreement is obtained if the nuclear force includes a tensor part. The bulk of the cancellation of the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ beta decay matrix element takes place within the $s^4{p}^{10}$ configuration. In general, configuration mixing is of secondary importance; its most noticeable effect is on the $M1\mathrm{}$ decay of the first-excited state of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$.