Shell model and band structures in 19O

Oertzen, W. von; Milin, Matko; Dorsch, T.; Bohlen, H.G.; Krücken, R.; Hertenberger, R.; Kokalova, Tz.; Mahgoub, M.; Wheldon, C.; Wirth, H.‐F.

doi:10.1140/epja/i2010-11060-7

Cited by 13 publications

(18 citation statements)

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“…Their placement in the level scheme (Figure 1 Because the intensities of the γ lines from the unbound 4330 (3), 4943 (4), 4990 (4), 5232 (5), 5360 (3), and 6109 (4) keV levels are comparable to the decays from the bound ones, their decays must be predominantly radiative. Five of the six γ decays come from levels which correspond in energy within uncertainties to some of the states reported in a comprehensive study of the 13 C( 7 Li,p) reaction [18]. However, widths above 4 keV without uncertainties are quoted for all states above S n in that paper, including values of 5 to 13 keV for the five states observed in the present work to γ decay.…”

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confidence: 50%

“…Five of the six γ decays come from levels which correspond in energy within uncertainties to some of the states reported in a comprehensive study of the 13 C( 7 Li,p) reaction [18]. However, widths above 4 keV without uncertainties are quoted for all states above S n in that paper, including values of 5 to 13 keV for the five states observed in the present work to γ decay.…”

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confidence: 50%

“…Some of the spin parity suggestions differ from those of previous works [12,18]. However, the previous spin parity suggestions were based solely on empirical methods such as total cross sections and 2J + 1 analysis in Ref.…”

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confidence: 93%

“…In spite of this record, we were surprised to discover that six states from 368 to 2147 keV above the neutron threshold decay predominantly or totally by γ radiation (Figure 1). Five of these states had been previously reported [12,18] This was the first study of 19 O using a heavy-ion fusion reaction which favors population of higher-spin states and employs a modern γ detector array. The α-γ and mostly α-γ-γ coincidences were analyzed to build upon the previously known level and decay scheme.…”

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confidence: 99%

“…The importance of 19 O with a closed major proton shell and an exactly halffilled neutron d 5/2 orbital has been recognized with over half a century of investigations [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In spite of this record, we were surprised to discover that six states from 368 to 2147 keV above the neutron threshold decay predominantly or totally by γ radiation (Figure 1).…”

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Radiative decay of neutron-unbound intruder states inO19

et al. 2016

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The 9 Be( 14 C, αγ) reaction at E Lab =30 and 35 MeV was used to study excited states of 19 O. The Florida State University (FSU) γ detector array was used to detect γ radiation in coincidence with charged particles detected and identified with a silicon ∆E-E particle telescope. Gamma decays have been observed for the first time from six states ranging from 368 to 2147 keV above the neutron separation energy (S n =3962 keV) in 19 O. The γ decaying states are interspersed among states previously observed to decay by neutron emission. The ability of electromagnetic decay to compete successfully with neutron decay is explained in terms of neutron angular momentum barriers and small spectroscopic factors implying higher spin and complex structure for these intruder states. These results illustrate the need for complementary experimental approaches to best illuminate the complete nuclear structure. 1The decay mode(s) of a nuclear quantum state is (are) one of its most important properties after energy. Usually nuclear decay follows the hierarchy of the fundamental forces of nature.Decay by emission of one or more particles mediated by the strong nuclear interaction is normally the dominant mode for those states unbound to particle emission. Bound excited states usually decay by emission of electromagnetic radiation to the ground state. The ground state, in turn, decays much more slowly by β decay mediated by the weak nuclear interaction until the lowest energy neutron-to-proton ratio has been reached. Of course, there are exceptions: lower energy charged particle decay from unbound states is inhibited by the Coulomb barrier, and large spin change or low emission energy can inhibit γ decay so much that β decay occurs first. Even decay by neutrons which face no Coulomb barrier can be inhibited by large spin change, as is well known in high-spin spectroscopy of medium and heavy nuclei. However, based on the simple picture of barrier penetrability, neutron decay is usually assumed to dominate over radiative decay when angular momentum barriers are not very high. But Fermi's Golden Rule [1] states that the decay rate is the product of the coupling strength, the density of final states, and the matrix element between the wavefunction of the parent state and the daughter state (usually called spectroscopic factor (S)). What is often overlooked is that this latter factor due to the nuclear structure may be more instrumental than the angular momentum barrier in limiting neutron decay rates below those of electromagnetic decay. Examples are states with complex structure often involving intruder configurations.The role of factors beyond barrier penetrability is highlighted by observations reported in this paper of the decays of unbound states in 19 O populated in the 9 Be( 14 C,αγ) reaction which favors higher-spin states, which are typically more complex and may involve intruder configurations. The importance of 19 O with a closed major proton shell and an exactly halffilled neutron d 5/2 orbital has been recognized wi...

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confidence: 99%