Upper Limit to the Magnetic Moment of He-6

Authors(s):E. D. Commins and P. Kusch Publication:Physical Review Letters Publication Date:September 15, 1958 Publisher: American Physical Society Citation:Phys. Rev. Lett. 1, 208 Link:https://doi.org/10.1103/PhysRevLett.1.208

An experiment has been performed to place an upper limit on the nuclear magnetic moment of He6. Since this nucleus is even-even it is highly probable on theoretical grounds alone that the spin and magnetic moment are zero. Nevertheless there exists a disagreement between theory and experiment concerning the nature of the Gamow-Teller interaction in the He6 beta-decay. The disagreement might arise from experimental errors and there is some evidence that this is the case. On the other hand it has been suggested that the disagreement might arise from a failure of the assumption that He6 has zero spin.Consequently it is desirable to test this assumption experimentally.

It therefore seems highly probable on experimental grounds that the spin of the He nucleus is indeed zero.


We gratefully acknowledge the aid given us by J. Vise and B. M. Rustad, who designed, constructed and operated the gas-handling system and provided much useful advice. Joseph Haas expertly constructed the atomic beams apparatus, and A. Franklin assisted in taking data and performing calculations.


1 R.P. Feynman and M. Gell-Mann, Phys. Rev. 109, 193 (1958).

2 B. M. Rustad and S. L. Ruby, Phys. Rev. 97, 991 (1955)

3 B. M. Rustad and S. L. Ruby, post-deadline paper given at 1958 Annual Meeting of the American Physical Society.

4 Hermannsfeldt, Burman, Stahelin, Allen, and Braid, Phys. Rev. Lett. 1, 61 (1958). The work of these authors indicates that the He6 beta-decay interaction is axial vector, in agreement with Feynman and Gell-Mann, and in disagreement with Rustad and Ruby.

We are indebted to J. Vise and B. Rustad for the careful determination of the half-life of the current sample of He6.