The b-unstable nuclei 32,34,36,38 Si have been produced by projectile fragmentation and studied by inbeam Coulomb excitation. Excited states at 1399 6 25 keV and 1084 6 20 keV have been identified for the first time in 36 Si and 38 Si, respectively, and tentatively assigned J p 2 1 . The B͑E2; 0 1 1 ! 2 1 1 ͒ values leading to these states and the previously identified 2 1 1 states in 32,34 Si have been measured, and are compared to shell model calculations. Our results indicate that the 2 1 1 state in 34 Si has a large fp-shell intruder component, and that the 2 1 1 states in the N . 20 silicon isotopes can be reproduced assuming an N 20 shell closure. [S0031-9007(98)
The γ -ray spectroscopy of 25 Si and 29 S has been performed using single neutron knockout reactions with intermediate energy beams of the exotic isotopes 26 Si and 30 S. Two γ rays have been observed in 25 Si and three in 29 S. These are the first γ rays observed in these two isotopes. These two nuclei appear to be well deformed, and possible future intermediate-energy Coulomb excitation measurements would confirm their rotational nature.
Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have been studied using intermediate-energy beams of neutron-deficient 34 Ar, 30 S, and 26 Si. The inclusive cross sections, and also the partial cross sections for the population of individual bound final states of the 32 Ar, 28 S and 24 Si knockout residues, have been determined using the combination of particle and γ -ray spectroscopy. Similar to the two-proton knockout mechanism on the neutron-rich side of the nuclear chart, these two-neutron removal reactions from already neutron-deficient nuclei are also shown to be consistent with a direct reaction mechanism.
We report on the observation of excited states in the neutron-deficient phosphorus isotopes 26,27,28 P via in-beam γ-ray spectroscopy with both high-efficiency and high-resolution detector arrays. In 26 P, a previously-unobserved level has been identified at 244(3) keV, two new measurements of the astrophysically-important 3/2 + resonance in 27 P have been performed, γ decays have been assigned to the proton-unbound levels at 2216 keV and 2483 keV in 28 P, and the γ-ray lineshape method has been used to make the first determination of the lifetimes of the two lowest-lying excited states in 28 P. The expected Thomas-Ehrman shifts were calculated and applied to levels in the mirror nuclei. The resulting level energies from this procedure were then compared with the energies of known states in 26,27,28 P.
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