Selected Citation

Gamow-Teller Interaction in the Decay of He6

Authors(s):B. M. Rustad and S. L. Ruby Publication:Physical Review Publication Date:February 15, 1955 Publisher: American Physical Society Citation:PhysRev.97.991 Link:

The coefficient α in the electron-neutrino angular correlation W(φ)=1+α(p/W) cosφ] for the He6—Li6 transition has been determined by measuring the coincidence rate between recoil ions and beta rays of selected energy as a function of the angle between the particles. Since the decay oi He6 (allowed ft value and ΔI=1) obeys only Gamow-Teller selection rules, the interaction Hamiltonian for this transition is speci6ed completely by (GΑ+GΤ). The measured values of the correlation coeflicient are α=+0.36 +0. 11 for beta rays with mean energy 1. 25 Mev and o.2. 0=+0. 31+0.14 for the mean energy 2. 0 Mev. These results are compared with O. p=+~ 'and exp= — predicted from the pure tensor and axial vector invariants, respectively. The limiting value set by the experiment for (Gz/Gr) together with the observed absence of the Fierz interference terms for allowed beta spectra proves that the tensor invariant is dominant in the beta-decay interaction of He6.

[Results] provide convincing evidence against the combinations (T,A) and the less probable (S,V). These two important observations reduce the possible combinations to (S,T), (S,A), (U, T), and (V,A) with the inclusion of P undecided. Similar arguments, though less certain, against the combinations (S,A) and (U,T) have been advanced by Mahmoud and Konopinski, which are based on the observed statistical shape of first forbidden spectra. The present identification of T as the Gamow-Teller invariant further narrows the possibilities for the beta-decay allowed spectra interaction to a form containing either the (S,T) or the less probable (V,T) combination of invariants.


The authors wish to express their appreciation to Professor W. W. Havens, Jr. and Professor C. S. Wu for their many helpful suggestions and stimulating discussions during the course of this work. It is a pleasure to acknowledge the cordial hospitality of the Brookhaven National Laboratory. In particular, we wish to thank Dr. M. Fox and the Reactor Group for assistance in making bombardments.