Lifetime measurements with the Doppler shift attenuation method using a thick homogeneous production target - verification of the method

Doppler Shift Attenuation Method (DSAM) analysis of excited-state lifetimes normally employs thin production targets mounted on a thick stopper foil ('backing') serving to slow down and stop the recoiling nuclei of interest in a well-defined manner. Use of a thick, homogeneous production target leads to a more complex analysis as it results in a substantial decrease in the energy of the incident projectile which traverses the target with an associated change in the production cross section of the residues as a function of penetration depth. Here, a DSAM lifetime analysis using a thick homogeneous target has been verified using the Doppler broadened lineshapes of γ rays following the decay of highly excited states in the semi-magic (N = 50) nucleus ⁹⁴Ru. Lifetimes of excited states in the ⁹⁴Ru nucleus have been obtained using a modified version of the LINESHAPE package from the Doppler broadened lineshapes resulting from the emission of the γ rays, while the residual nuclei were slowing down in the thick (6 mg/cm²) metallic ⁵⁸Ni target. The results have been validated by comparison with a previous measurement using a different (RDDS) technique. (authors)