On the relationship between the deuteron form factors and the physical $S$-matrix. III

The relativistic Jost matrix of neutron-proton scattering with total intrinsic angular momentum unity and positive parity is expressed in terms of the physical $n-p$- scattering phases. On the physical sheet a pole is introduced in the Jost matrix which corresponds to the deuteron state with allowance for a $d$-wave admixture. The electromagnetic form factors of the $n-p$-system are analytically continued to the point of the deuteron pole. The results obtained are used to express the electromagnetic form factors of the deuteron in terms of the single-nucleon form factors and integrals over the physical region of the $n-p$ scattering phases.