Anomalously Hindered E2 Strength B(E2;21+→0+) in C16 (original) (raw)
2004, Physical Review Letters
The electric quadrupole transition from the first 2 + state to the ground 0 + state in 16 C is studied through measurement of the lifetime by a recoil shadow method applied to inelastically scattered radioactive 16 C nuclei. The measured lifetime is 75 ± 23 ps, corresponding to a B(E2; 2 + 1 → 0 + ) value of 0.63 ± 0.19 e 2 fm 4 , or 0.26 ± 0.08 Weisskopf units. The transition strength is found to be anomalously small compared to the empirically predicted value. PACS numbers: 23.20.Js, 21.10.Tg, 29.30.Kv Quadrupole strengths are fundamental quantities in probing the collective character of nuclei. The enhancement of the electric quadrupole (E2) transition strength with respect to that of single proton excitation may reflect large fluctuation or deformation of nuclear charge [1]. One of the important E2 transitions in an even-even nucleus is that from the first 2 + (2 + 1 ) state to the ground state (0 + g.s. ), the reduced transition probability B(E2) of which has long been a basic observable in the extraction of the magnitude of nuclear deformation or in probing anomalies in the nuclear structure. With recent advances in techniques for supplying intense beams of unstable nuclei, several exotic properties such as magicity loss have been discovered in neutron-rich nuclei through measurements of E2 strengths.
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1.1 General survey It is customary to regard nuclear physics as the field of study that includes the structure of atomic nuclei, the reactions that take place between them, and the techniques, both experimental and theoretical, that shed light on these subjects. Rigid adherence to such limits would, however, exclude much that is both exciting and informative. The nucleus entered physics as a necessary component of the atomic model and nuclear effects in spectroscopy and solid state physics now provide not only elegant methods for determination of nuclear properties but also convincing demonstrations of the powers of quantum mechanics. Equally, those particles sometimes described as elementary or fundamental, although first recognized in the cosmic radiation, soon assumed a role of importance in nuclear problems, especially in the understanding of the forces between neutrons and protons. Advances in the study of particles, or sub-nuclear physics, besides leading to the discovery of new and previously unsuspected physical laws, have frequently stimulated back-reference to complex nuclei
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