Meson-exchange currents in thermal n-3He radiative capture

The cross section for radiative capture of thermal neutrons by ³He arising from 1π, 1ρ and 1ω meson-exchange processes is calculated using oscillator and exponential wave functions for ³He (including a D-wave component) and oscillator wave functions for ⁴He (also including a D-wave component). A correlation function with a range of 0.25 fm is incorporated in the wave function to describe the short-range behaviour. Results are sensitive to the assumed range of the correlation function and to the triplet scattering length in the neutron scattering wave function, which are not known accurately. For a reasonable set of parameter choices, a combination of one-body impulse approximation (between D-states) and two-body meson-exchange current processes can explain the entire experimental cross section.