New Region of Deformation: The Neutron-Rich Sulfur Isotopes

Scheit, H.; Glasmacher, T.; Brown, B. A.; Brown, J.; Cottle, P. D.; Hansen, P. G.; Harkewicz, Richard; Hellström, M.; Ibbotson, R. W.; Jewell, J. K.; Kemper, K. W.; Morrissey, D. J.; Steiner, M.; Thirolf, P. G.; Thoennessen, M.

doi:10.1103/physrevlett.77.3967

Cited by 283 publications

(247 citation statements)

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“…The nuclei in this region have been reported to show a wide variety of shapes, including evidence for shape coexistence [5,6] and superdeformation [7]. Shell model calculations have kept pace with experimental developments both to predict and understand the evolution of such structure away from stability.…”

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confidence: 99%

“…Shell model calculations have kept pace with experimental developments both to predict and understand the evolution of such structure away from stability. The sdf p effective interaction [8], among others, has been successfully used to explain regions of deformation like that observed in 42 Si 28 [1,9], the neutron-rich Sulphur isotopes [5,6] and the evolution of the spin-orbit splitting around N = 28 [10]. The present work, in addition to increasing our understanding of cross-shell excitations around the double "magic" 48 Ca, is motivated by the search and understanding of the existence of nuclei having a triaxial ellipsoid shapes in this region [11].…”

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confidence: 99%

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Structure of Neutron-Rich Ar Isotopes BeyondN=28

et al. 2008

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Structure of Neutron-Rich Ar Isotopes BeyondN=28

et al. 2008

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“…The evolution of the shell closures far from stability is, however, a subject of intense scrutiny. In particular, experimental studies have shown a breaking of magicity of the N = 20 [1][2][3] and the N = 28 [4,5] configurations for neutron-rich nuclei. Key nuclei in their respective regions, such as 32 Mg and 44 S, display large quadrupole collectivity arising from their prolate deformation.…”

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β decay ofNa32

et al. 2007

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The β-decay of 32 Na has been studied using β-γ coincidences. New transitions and levels are tentatively placed in the level scheme of 32 Mg from an analysis of γ -γ and β-γ -γ coincidences. The structure of nuclei along the valley of stability is well understood in terms of the traditional magic numbers, corresponding to large gaps in single-particle energy levels of nucleons in realistic mean-field theories including a spin-orbit interaction. The evolution of the shell closures far from stability is, however, a subject of intense scrutiny. In particular, experimental studies have shown a breaking of magicity of the N = 20 [1][2][3] and the N = 28 [4,5] configurations for neutron-rich nuclei. Key nuclei in their respective regions, such as 32 Mg and 44 S, display large quadrupole collectivity arising from their prolate deformation. Over the years (and with the steady increase of computing power), shell model calculations have led to a better understanding of the magicity disappearance in certain regions of the nuclear chart (for a recent review, see Ref.[6] and references therein). In the case of the N = 20 shell closure, the so-called "island of inversion" around 32 Mg is due to low energy fp-intruder states competing with the standard sd-orbitals, giving rise to the deformed configurations.Despite many experimental studies, significant features of the 32 Mg level scheme are still unknown. In fact, only the first excited state at 885 keV is firmly assigned as a 2 + state [7]. The other excited states have, at best, only received a tentative assignment. Of interest is the location of the 4 + state to shed

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“…), 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 [2,3,4] have been discovered in neutron-rich nuclei through measurements of E2 strengths.The present Letter reports lifetime measurements of the 2 + 1 state of the neutron-rich nucleus 16 C. The lifetime is inversely proportional to B(E2). A simple model of a nucleus as a quantum liquid-drop well describes the systematic tendency that B(E2) varies in inverse proportion to the excitation energy E(2 + 1 ) of the 2 + 1 state [5].…”

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Anomalously HinderedE2StrengthB(E2;21+→0+

et al. 2004

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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 [2,3,4] have been discovered in neutron-rich nuclei through measurements of E2 strengths.The present Letter reports lifetime measurements of the 2 + 1 state of the neutron-rich nucleus 16 C. The lifetime is inversely proportional to B(E2). A simple model of a nucleus as a quantum liquid-drop well describes the systematic tendency that B(E2) varies in inverse proportion to the excitation energy E(2 + 1 ) of the 2 + 1 state [5]. For carbon isotopes, when N changes from the magic number 8 to 10, E(2 + 1 ) decreases dramatically from 7.012 to 1.766 MeV [6]. It can then be anticipated that 16 C (N = 10) would have a much larger B(E2) than that of * Electronic address: imai@rarfaxp.riken.go.jp † On leave from ATOMKI, Debrecen, Hungary. ‡ Present address: NSCL Michigan State University, East Lansing, Michigan 48824, USA.14 C (N = 8). Unexpectedly, a remarkably small B(E2) was found for 16 C in the present work. The observed value, in Weisskopf units, turns out to be far smaller than any other B(E2) measured on the nuclear chart.In the present experiment, a new technique was employed to measure the lifetime of an excited state populated in inverse-kinematics reactions. The technique essentially followed the concept of the recoil shadow method (RSM) [7], in which the emission point of the de-excitation γ-ray is located and the γ-ray intensity is recorded as a function of the flight distance of the deexciting nucleus. As the flight velocity of the de-exciting nucleus is close to half the velocity of light, the flight distance over 100 ps corresponds to a macroscopic length of about 1.7 cm. Thus, the present shadow method provides a wide range of applicability, extending to lifetimes of as short as a few tens of ps. In particular, the method is useful for determining the B(E2) value of Z < 10 nucl...

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New Region of Deformation: The Neutron-Rich Sulfur Isotopes

Cited by 283 publications

References 19 publications

Structure of Neutron-Rich Ar Isotopes BeyondN=28

Structure of Neutron-Rich Ar Isotopes BeyondN=28

β decay ofNa32

Anomalously HinderedE2StrengthB(E2;21+→0+

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