Elsevier

Nuclear Physics A

Volume 246, Issue 1, 14 July 1975, Pages 231-245
Nuclear Physics A

Recoil-distance lifetime measurements of low-lying states of 21Ne, 24Na, 25Mg and 42K with the B+ 16O and 26Mg+ 18O reactions

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Abstract

The recoil-distance method has been used in conjunction with the B+ 16O and 26Mg+ 18O reactions to measure mean lives of low-lying states of 21Ne, 24Na, 25Mg and 42K. The following results are obtained: 21Ne, Ex = 0.35 MeV, τm = 12.9 ± 1.6ps; 24Na, 0.56 MeV, 46 ± 6 ps; 25Mg, 0.97 MeV, 16.9 ± 1.0 ps; 42K, 0.11 MeV, 410 ± 60 ps; 0.26 MeV, 192 ± 13 ps; 0.70 MeV, 59 +- 11 ps and 1.38 MeV, 1690 +- 120ps. Excitation energies and branching ratios for 42K levels are given. Combination of γ-γ coincidences on 2 ns delayed γ-rays and the recoil-distance data establish a hitherto unobserved 42K level at an excitation energy of 1375.5 ± 0.2 keV. This level, which decays exclusively to the 699 keV, Jπ = (5) level, is tentatively assigned the stretched isospin configuration [(1d32−2)01(1f724)6+, 1]6 +, 2. A calculation with a weak-coupling model supports this assignment.

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    University of Lund, Lund, Sweden.

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