Low-energy theorems for nuclear compton and raman scattering and 0 + → 0 + two-photon decays in nuclei

Abstract

Low-energy theorems for elastic photon scattering (nuclear Compton scattering) from a nucleus of arbitrary spin are derived in the nonrelativistic approximation through terms quadratic in the photon frequency. The same derivation is made for the special case of 0 + → 0 + nuclear excitation by inelastic photon scattering (nuclear Raman scattering). Use is made of the general principle of gauge invariance, which bypasses the need to specify the form of the current operator explicitly. A general discussion of the contribution of mesonic exchanges is made and their effect is isolated. The center-of-mass correction to the nuclear diamagnetic susceptibility is calculated. The 0 + → 0 + two-photon decay amplitude is obtained from the nuclear Raman amplitude and the transition rate is calculated.