Integral- and differential-decay-curve methods for recoil distance measurements of nuclear lifetimes

A new procedure of analysis for the measurement of nuclear lifetimes with the Recoil Distance Method is presented and discussed. In comparison with the standard Differential Decay Curve method, the new procedure avoids the difficulties related to the variation of the average velocity of decaying nuclei with the target–stopper distance, which can result from a large spread in the angular and velocity distributions. This can be particularly useful when a relatively thick target must be used due to the weak beam current, as in measurements with radioactive beams. Moreover the “integral” form of the method can be useful when the most significant points lie at the border of the explored region, where the evaluation of derivatives is subject to larger uncertainties.