Neutron-Proton Bremsstrahlung Calculations

Abstract

The neutron-proton bremsstrahlung cross section between 14 and 208 MeV is calculated by including the external radiation terms to all orders in the momentum of the photon, $K$, and by using the low-energy theorem to compute the internal scattering contribution to order ${K}^{0}$. These calculations, which employ a simple off-shell calculations of the elastic phase shifts, are in good agreement with the data at 208 MeV. These off-shell calculations are also compared to calculations using the corresponding on-shell phase shifts in order to determine the strength of the off-shell terms. In coplanar scattering where ${\ensuremath{\theta}}_{p}+{\ensuremath{\theta}}_{n}\ensuremath{\le}\ensuremath{\sim}60\ifmmode^\circ\else\textdegree\fi{}$, these off-shell effects constitute as much as 50% or more of the cross section, while for $60\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}{\ensuremath{\theta}}_{p}+{\ensuremath{\theta}}_{n}\ensuremath{\le}90\ifmmode^\circ\else\textdegree\fi{}$, the offshell contributions are much smaller.