| Popis: |
The recoil-distance method has been used in conjunction with the B+ 16 O and 26 Mg+ 18 O reactions to measure mean lives of low-lying states of 21 Ne, 24 Na, 25 Mg and 42 K. The following results are obtained: 21 Ne, E x = 0.35 MeV , τ m = 12.9 ± 1.6ps; 24 Na , 0.56 MeV , 46 ± 6 ps ; 25 Mg , 0.97 MeV , 16.9 ± 1.0 ps ; 42 K , 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 42 K levels are given. Combination of γ-γ coincidences on 2 ns delayed γ-rays and the recoil-distance data establish a hitherto unobserved 42 K level at an excitation energy of 1375.5 ± 0.2 keV. This level, which decays exclusively to the 699 keV, J π = (5) − level, is tentatively assigned the stretched isospin configuration [(1d 3 2 −2 ) 01 (1f 7 2 4 ) 6+, 1 ] 6 +, 2 . A calculation with a weak-coupling model supports this assignment. |
