The recoil shadow anisotropy method

The Recoil Shadow Anisotropy Method (RSAM) is a new experimental method for identifying isomers in the nanosecond range and measuring their half-lives. This method can be applied to experiments performed with thin targets and gamma -ray multidetector arrays including collimated composite detectors and does not require any additional device. It uses the shadow effect imposed by the collimators on the different elements of composite detectors for gamma -rays emitted by recoiling nuclei. RSAM was developed for the clover detectors of the Eurogam-2 array and tested using several data sets obtained with this array. A number of known isomers with half-lives lying between 0.9 and 18 ns in Hg-194, Au-191, Gd-148, Gd-149, Pb-193 and Pb-194 have been successfully re-measured, proving the ability of RSAM for lifetime measurements. (C) 2001 Elsevier Science B.V. All rights reserved.