Isospin-Forbidden Particle Decays of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mo>=</mo><mfrac><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></mfrac></math></span> Levels in Mirror Nuclei

E. G. Adelberger; A. B. McDonald; C. L. Cocke; C. N. Davids; A. P. Shukla; H. B. Mak; D. Ashery

doi:10.1103/PhysRevC.7.889

Isospin-Forbidden Particle Decays of $T = \frac{3}{2}$ Levels in Mirror Nuclei

E. G. Adelberger, A. B. McDonald, C. L. Cocke, C. N. Davids, A. P. Shukla, H. B. Mak, and D. Ashery

Phys. Rev. C 7, 889 – Published 1 March 1973

Abstract

Absolute branching ratios for the isospin-forbidden particle decays of the lowest $T = \frac{3}{2}$ levels of ${}^{13}C$ , ${}^{13}N$ , ${}^{17}O$ , and ${}^{17}F$ have been measured by populating the levels in ( ${}^{3}{He}$ , $p$ ), ( ${}^{3}{He}$ , $α$ ), or ( ${}^{3}{He}$ , $n$ ) reactions and observing the resulting decay products in coincidence. Branching ratios of 0.070 ± 0.018, 0.261 ± 0.030, and 0.026 ± 0.018 (0.236 ± 0.012, 0.150 ± 0.010, 0.053 ± 0.015) were determined for the neutron (proton) decays of the 15.1-MeV, $T = \frac{3}{2}$ level of ${}^{13}C$ ( ${}^{13}N$ ) to the ground state and first two excited states of ${}^{12}C$ , respectively. Branching ratios of 0.91 ± 0.15 and 0.05 ± 0.02 (0.088 ± 0.016, 0.23 ± 0.05) were determined for the neutron (proton) decays of the 11.08-(11.20-) MeV, $T = \frac{3}{2}$ level of ${}^{17}O$ ( ${}^{17}F$ ) to the ground state and unresolved 6.05- and 6.13- MeV excited states of ${}^{16}O$ , respectively. The $α$ -decay branching ratios of the 15.1-MeV, $T = \frac{3}{2}$ level of ${}^{13}N$ to the ground state and first two excited states of ${}^{9}B$ were determined to be 0.049 ± 0.027, 0.039 ± 0.039, and 0.072 ± 0.045, respectively. Possible origins of the large asymmetries observed in the nucleon decays of these analog levels are discussed. The value obtained for $\frac{Γ_{p_{0}}}{Γ}$ for the lowest $T = \frac{3}{2}$ level of ${}^{13}N$ may be combined with ${}^{13}C (e, e^{'})$ and ${}^{12}C (p, γ) {}^{13}N$ measurements to determine the ratio $\frac{Γ_{γ}^{M 1} ({}^{13}C)}{Γ_{γ}^{M 1} ({}^{13}N)} = 1.0 \pm 0.2$ for $γ$ decay to the ground state. This places an upper limit on the isotensor transition matrix element at 7% of the isovector matrix element.

Received 9 October 1972

DOI:https://doi.org/10.1103/PhysRevC.7.889

Authors & Affiliations

E. G. Adelberger^*

California Institute of Technology and Princeton University

A. B. McDonald^†

A. E. C. L. Chalk River Nuclear Laboratories, and California Institute of Technology

C. L. Cocke^‡, C. N. Davids^§, A. P. Shukla^∥, H. B. Mak, and D. Ashery^¶

California Institute of Technology, Pasadena, California

^*Present address: Physics Department, University of Washington, Seattle, Washington 98195.
^†Present address: Nuclear Physics Branch, AECL, Chalk River Nuclear Laboratories, Chalk River, Ontario, Canada KOH 1JO.
^‡Present address: Physics Department, Kansas State University, Manhattan, Kansas 66502.
^§Present address: Physics Department, University of Texas, Austin, Texas 78712.
^∥Present address: Physics Department, India Institute of Technology, Kanpur, V. P., India.
^¶Present address: Tel-Aviv University, Tel-Aviv, Israel.

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Vol. 7, Iss. 3 — March 1973

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