P. D. Cottle

Collectivity in 44S

Abstract The energy and reduced transition probability B(E2; 0g.s.+ → 2+) for the lowest excited state in the neutron-rich isotope 1644S28 were measured by intermediate-energy Coulomb excitation. The excitation energy is E(2+) = 1297(18) keV and the reduced transition probability is B(E2; 0g.s.+ → 21+) = 314(88) e2fm4. The experimental results are compared with self-consistent mean-field calculations and shell model calculations with empirical interactions. The shell model calculations indicate that the large B(E2) value in 44S is vibrational in origin, while the neighboring isotopes 40,42S are statically deformed.

Role of intruder configurations in 26,28Ne and 30,32Mg

Abstract The energies and reduced transition probabilities B(E2;0g.s.+→2+) for the lowest Jπ=2+ excited states in the neutron-rich radioactive isotopes 26,28 Ne and 30,32 Mg were measured via intermediate energy Coulomb excitation. The data suggest that the interaction between coexisting 0ℏω (normal) and 2ℏω (intruder) configurations significantly perturbs the energy of the 21+ state in 28 Ne, while the data on 26 Ne and 30 Mg can be well understood in the context of 0ℏω configurations alone. Nilsson model calculations suggest that if these nuclei have static axially symmetric deformations, they are prolate.

Spectroscopy of the 21+ state in 22O and shell structure near the neutron drip line

Abstract The energy and electromagnetic matrix element B(E2↑) for the 21+ state in 22O have been determined via inelastic scattering of a beam of these radioactive nuclei from a 197Au target. These results provide strong evidence for the existence of the N=14 subshell closure in 22O. This demonstrates that the shell structure in 22O is similar to that of stable oxygen isotopes, even though this nucleus is only two neutrons away from the neutron drip line. These results are reproduced in the standard sd shell model as well as with a an expanded space which also includes the f7/2 and p3/2 orbitals.

'Magic' nucleus 42Si.

Nuclear shell structures—the distribution of the quantum states of individual protons and neutrons—provide one of our most important guides for understanding the stability of atomic nuclei. Nuclei with ‘magic numbers’ of protons and/or neutrons (corresponding to closed shells of strongly bound nucleons) are particularly stable. Whether the major shell closures and magic numbers change in very neutron-rich nuclei (potentially causing shape deformations) is a fundamental, and at present open, question. A unique opportunity to study these shell effects is offered by the 42Si nucleus, which has 28 neutrons—a magic number in stable nuclei—and 14 protons. This nucleus has a 12-neutron excess over the heaviest stable silicon nuclide, and has only one neutron fewer than the heaviest silicon nuclide observed so far. Here we report measurements of 42Si and two neighbouring nuclei using a technique involving one- and two-nucleon knockout from beams of exotic nuclei. We present strong evidence for a well-developed proton subshell closure at Z = 14 (14 protons), the near degeneracy of two different (s1/2 and d3/2) proton orbits in the vicinity of 42Si, and a nearly spherical shape for 42Si.

Proton scattering on the radioactive nucleus 20O and the 0gs+→21+ transition in the neutron-rich oxygen isotopes

Abstract Elastic and inelastic proton scattering to the 21+ state of the single closed shell radioactive nucleus 20 O have been measured in inverse kinematics with a beam energy of 30 MeV/u. The matrix element determined for the 0gs+→21+ transition in this work is compared with the corresponding electromagnetic matrix element to determine the ratio of the neutron and proton multipole matrix elements for this transition, Mn/Mp=2.9(4), which is quite different from the value Mn/Mp=N/Z=1.5 that would be expected for a purely isoscalar transition. A comparison of this result to a corresponding result for 18 O suggests that the strength of the core polarizing interactions between the valence neutrons and the core protons and neutrons is changing significantly with mass.

Two-neutron knockout from neutron-deficient Ar-34, S-30, and Si-26

Department of Physics, School of Electronics and Physical Sciences,University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom(Dated: February 8, 2008)Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have beenstudied using intermediate-energy beams of neutron-deficient

Extreme \( \alpha\) -clustering in the 18O nucleus

The structure of the 18O nucleus at excitation energies above the

Possible unified interpretation of low-lying negative parity states in lanthanide and actinide regions

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Shell structure at N=28 near the dripline: Spectroscopy of Si-42, P-43, and S-44

decay threshold was studied using 14C +

Cooperative Learning in the Tutorials of a Large Lecture Physics Class.

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