Microscopic Study of $\alpha +N$ Bremsstrahlung from Effective and Realistic Multi-nucleon Interactions

Based on an effective nucleon-nucleon interaction, a microscopic cluster model of the nucleus-nucleus bremsstrahlung, including implicitly a part of the effects of meson-exchange currents via an extension of the Siegert theorem is applied to the $\alpha +p$ and $\alpha +n$ systems. The contributions of the $E1$ and $E2$ transitions to the bremsstrahlung cross sections are evaluated and their relative importance for the mirror systems $\alpha +p$ and $\alpha +n$ is compared. Another approach based on realistic two- and three-nucleon interactions and the No-Core Shell Model/Resonating-Group Method is also investigated. Some preliminary results for the $\alpha +p$ bremsstrahlung are displayed.