NUCLEAR MOMENTS AND ISOMERIC SHIFT OF SHORT-LIVED NUCLEAR LEVELS BY RESONANT SCATTERING

In a resonant scattering experiment the perturbation of the angular distribution by a magnetic field perpendicular to the scattering plane depends, due to the finite bandwidth of the incident gamma-ray, on the spins and parities of both nuclear levels and on the mixing ratio of the γ-transition. It is shown that for certain conditions, however, this dependence can be neglected and one finds a situation similar to the perturbed γ-γ angular correlation. These conditions are: (1) The lifetime τ of the excited nuclear state must be short enough so that the perturbation can be neglected in second order. (2) The source must not be moving relative to the target. The influence of the quadrupole interaction on the angular distribution is calculated up to second order for a 0+→2+ E2 transition. It is shown, that in contrast to the perturbed γ-γ angular correlation, the sign of the quadrupole interaction can be measured in the case of resonant scattering from a single crystal, because the perturbation is of first order provided the incident gamma-ray is Doppler-shifted. © 1968 Springer-Verlag.