Influence of Different Backing Materials on Lifetimes in Doppler-Shift Measurements

The mean lives of the 2312-, 3947-, and 6203-keV levels of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ have been measured with the Doppler-shift-attenuation (DSA) method through the reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(p,\gamma ){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ($E_p=1.15\mathrm{}$ MeV) using C, Ti, Ag, Mo, Ni, Ta, Au, and W as stopping materials. ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ ions were separated both onto and into the backings. The results show in this case about ±20% anomalies. Some sources of error arising from target preparation are discussed. In DSA measurements of short lifetime the use of implanted targets seems to be advantageous. The measured lifetimes are given as 70 ± 10, 10.5 ± 3.5, and 118 ± 13 fsec, respectively.