Gamma Ray Induced Doppler broadening and the determination of lifetimes of excited nuclear states

Abstract

Measurements of lifetimes of excited states in nuclei yield crucial information for sensitive tests of nuclear models. Here a novel method will be discussed which involves the GRID (Gamma Ray Induced broadening) technique, in which Doppler broadening is observed in a transition from a nucleus recoiling from the emission of a previous gamma ray. As the recoil energy is extremely small, ultra‐high energy resolving power has to be used. To date all such experiments have been carried out at ILL using the GAMS4 double flat crystal spectrometer which is operated in a NIST ILL collaboration. The method can be used for all lifetimes below a few picoseconds. The wide range of applicability, together with the very exhaustive set of data often obtained, is an advantage with respect to many other methods. The characteristic features of GRID will be discussed using some selected examples.