Comment on “Photon spectrum of the neutron-proton Bremsstrahlung at 170 MeV”: Contributions of np → dγ to inclusive photon energy spectra from np and pd collisions near 200 MeV

Several years ago, a measured photon energy spectrum from np collisions was presented as a measurement of free np Bremsstrahlung, and subsequently theoretical groups compared the data to their model calculations of the process np → npγ [F. Malek, A. Nifenecker, J.A. Pinston, F. Schussler, S. Drissi, J. Julien, Phys. Lett. B 266 (1991) 391]. We point out that in np collisions, np capture (np → dγ) is important and cannot be ignored. It contributes approximately 30% of the cross section for photons above 40 MeV. Capture also makes a significant contribution to the photon spectra produced in p-d collisions, and possibly has a role in p-nucleus collisions. In the former case, better agreement between theory and experiment is obtained when (quasifree) capture is included.