On the line-shape and lifetime determination in recoil distance Doppler-shift measurements

A method for the calculation of the gamma-ray line-shapes observed in recoi l distance Doppler-shift measurements of nuclear lifetimes is presented emp hasising the case where a gate is set on a transition which feeds directly the level of interest. A description of such coincidence spectra is propose d for the first time. It is shown that a successful reproduction of the dat a requires to take into account the emission of gamma-rays during the slowi ng-down of the ions in the stopper if the investigated lifetime is shorter than or comparable to the slowing-down time. The corresponding formalism fo r lifetime determination in the framework of the differential decay-curve m ethod is developed. The new approach is illustrated by an application to ex perimental data obtained in the Pd-110(Si-28, 4n)Nd-134 reaction at a beam energy of 125 MeV. (C) 1999 Elsevier Science B.V. All rights reserved.