Accurate measurements of E2 lifetimes using the coincidence recoil-distance method

Abstract

Mean lives of four E2 transitions in the (2s, 1d) shell have been measured using the recoil-distance method (RDM), γ-rays de-exciting the level of interest were detected in coincidence with particles detected in an annular detector at a backward angle thereby reducing the background and producing a beam of recoiling nuclei of well-defined energy and recoil direction. Lifetimes measured were: 22 Ne, 1.275 MeV level (2 + → 0 +), 5.16±0.13 ps; 26 Mg, 3.588 MeV level (0 + → 2 +), 9.29±0.23 ps; 30 Si, 3.788 MeV level (0 +→ 2 +), 12.00±0.70 ps; 38 Ar, 3.377 MeV level (0 + → 2 +), 34.5±1.5 ps . The present measurements are compared to those of previous investigators. For the 22Ne level, averaged results from four different measurement techniques are compared and found to be in good agreement. The experimental results are compared to shell-model calculations.