Electrodynamics of direct interparticle action. II. Relativistic treatment of radiative processes: F. Hoyle and J. V. Narlikar. Institute of Theoretical Astronomy, University of Cambridge, Cambridge, England

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This chapter discusses the three reactions where theory and experiment interact intermittently, and those are ND radiative capture, quasifree electron proton scattering in three-particle nuclei, and pion double charge exchange. The radiative ND capture reaction at low energies is fairly well understood. There are El transitions that depend on the D-states of the two- nucleon and three-nucleon bound states. However, the most important property is the long range parts of the D-state wave functions. The contribution to the isotropic term arises from Ml transitions that depend on the S1-state of the 3N bound state and are sensitive to meson exchange currents. The radiative capture of thermal neutrons in deuterium is a Ml transition. When the cross-section is calculated using the Ml operator given by only the nucleon spin and orbital magnetic moments, one finds a value of 0.15 mb, a discrepancy of a factor of 4. The experimental cross-section is obtained by including a phenomenological exchange operator with a magnitude consistent with the He3 and H3 magnetic moments. A more realistic representation of the meson exchange effects is possible and desirable. The chapter also describes an experiment on quasifree electron proton scattering in He3 and discusses an investigations on the pion double charge exchange reactions.