Abstract
One in about a few 10 5 sub-Coulomb d β t collisions is accompanied by the emission of a Ξ³ photon. The Ξ³ spectrum from these collisions is dominated by a 16.7 MeV peak, corresponding to the population of the p -wave 3 / 2 β Ξ± β n ground-state resonance in the E 1 transition from an intermediate d -wave Ξ± β n state, corresponding to the He 5 excited state around 16.7 MeV. The strength of this spectrum at the large Ξ³ -energy endpoint decreases fast both due to kinematic factors and due to centrifugal repulsion between neutron and Ξ± particle at near-zero relative energies. However, no centrifugal repulsion would occur if s -wave Ξ± β n states were populated in a magnetic dipole transition. Therefore, one can expect that close to the Ξ³ -spectrum endpoint around 17.5 MeV the M 1 transition could dominate, leading to additional counts in experimental spectra which could be easily misinterpreted as a background. This work presents calculations of the M 1 contribution to the d + t β Ξ± + n + Ξ³ cross section caused both by convection and magnetization currents. While the first contribution was found to be negligible, the one from magnetization depends strongly on the choice of the model for the d β t channel scattering wave function. Using d β t interaction models from the literature, represented either by a gaussian of by a square well, resulted in unrealistically strong M 1 contribution. Withoptical folding potential constructed in the present work, correctly representing the sizes of deuteron and triton, the M 1 contribution near the endpoint is reduced to about 2 % of the 16.7-MeV E 1 peak. Arguments in favor of more detailed calculations, that could potentially change this number, are put forward. Published by the American Physical Society 2024