Absorption of resonance scattered gamma-rays as a method of measuring nuclear level widths

A novel method for determining nuclear level widths is used in this investigation. Neutron capture gamma-rays from iron bombard a lead target. The incident 7.285 Mev gamma-rays cause resonance fluorescence of the Pb²⁰⁸ in the target. The energy of the emitted gamma-rays varies continuously with the scattering angle as the result of the recoil energy is about 500 ev. The energy resolution is so well defined that a level width can be determined by measuring the resonance depression caused by an absorber placed in the scattered beam. The method is applied to the known level in lead and as self-absorption preformed. Only a portion of the resonance depression was observed since it is located near 0°and small angle Compton scattering interferes with the signal. The value observed for the width was 0.7 ± 0.2 ev which agrees with the measurements performed by other methods. Applications of the technique are suggested which should be of substantial value to the nuclear spectroscopist