Threshold Effects inn−dScattering due to the Existence of the Di-Neutron

Use is made of a simple soluble model to evaluate the threshold effect which arises in the $n-d$ scattering cross section if the di-neutron exists. The model contains four parameters. They permit a large set of experimental data to be reproduced remarkably well. Various binding energies of the hypothetical di-neutron are assumed. The effect is a rounded step. Its height is about 20% of the total cross section for any reasonable value of the binding energy, if the value 8.26 F is assumed for the $n-d$ doublet scattering length.