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The structure and decay dynamics for 0+ and 2+ continuum excitations of 26O are investigated in a three-body 24O + n + n model. The validity of a simple approximation for the cross section profile for long-lived 2n emission is demonstrated. A sequence of three 0+ monopole ("breathing mode" type) excited states is predicted. These states could probably be interpreted as analogs of Efimov states pushed in the continuum due to insufficient binding. The calculated energies of the 2+ states are related to the excitation spectrum of 25O. We discuss the correlation between the predicted 26O spectrum and experimental observations. [ABSTRACT FROM AUTHOR]

The dynamic mechanism of the Thomas-Ehrman shift in three-cluster systems is studied by using the example of 16Ne and 16C isobaric mirror partners. We predict configuration mixings for 0+ and 2+ states in 16Ne and 16C. Large isospin symmetry breaking on the level of wave function component weights is demonstrated for these states and discussed as a three-body mechanism of the Thomas-Ehrman shift. It is shown that the description of the Coulomb displacement energies requires consistency among three parameters: the 16Ne decay energy ET, the F15 ground-state energy Er, and the configuration mixing parameters for the 16Ne and 16C0+ and 2+ states. Based on this analysis we infer the F151/2+ ground-state energy to be Er = 1.39-1.42 MeV. [ABSTRACT FROM AUTHOR]

The influence of the initial-state structure and the reaction mechanism on three-body decays is investigated using the example of the 6Be continuum populated in neutron-knockout reactions on 7Be. The sensitivity of the 6Be excitation spectrum and the three-body correlations to the different components of the model is demonstrated. It is shown that the spin composition of the initial state may have an overwhelming effect on the three-body continuum. The characteristics and structure of the second O2+ and 22+ states in 6Be are predicted and the conditions for their reliable observations are formulated. The effects of interference and the alignment of three-body states on the three-body correlations are demonstrated. [ABSTRACT FROM AUTHOR]

Previously unknown states in 18Na and 19Mg have been studied by measuring the trajectories of their decay products with microstrip detectors. Analyzing angular correlations of the fragments provided information on decay energies and widths of the parent states. The ground state of 18Na has been detected and its one-proton decay energy of 1.23(15) MeV determined. Four previously unknown states in 19Mg at 2.1, 2.9, 3.6, and 5.2 MeV have been observed. The competition between simultaneous and sequential two-proton emission of states in 19Mg is discussed, and the conclusion of a direct mechanism of 2p radioactivity of the 19Mg ground state is confirmed. [ABSTRACT FROM AUTHOR]

A theoretical method for estimates of a width of "true" four-nucleon decays is developed. Several candidate isotopes to possess this property are considered. Our lifetime estimates compare one-neutron, true two-neutron, and true four-neutron emissions at similar conditions. Prospects of experimental search for two-neutron, four-proton, and four-neutron radioactivity are discussed. [ABSTRACT FROM AUTHOR]

Structure with the lowest energy observed in the 10He spectrum populated in the proton knockout reaction with a 11 Li beam has a peak at 1.2 to 1.5 MeV. This peak is usually interpreted as a resonant 0+ ground state of l0He. Our theoretical calculations indicate that this peak is likely to be a superposition of 1~, 0+, and 2+ excitations with very similar shapes. Moreover, the "soft" 1" excitation appears to be the lowest in energy. Such an anomalous continuum response is traced to the halo structure of 11 Li providing an extreme low energy shift to all the expected continuum excitations. Competition between effects on the spectrum of the initial-state structure and of the final-state interaction and three-body correlations in l0He are discussed. The analogous effect of an extreme low-energy shift could also be expected in other cases of 2n emitters populated in reactions with halo nuclei. A simplified example of the 10He spectrum in a knockout from 14Be is given. We also discuss limits on the properties of 9He stemming from the observed l0He spectrum. [ABSTRACT FROM AUTHOR]

The article compares the effects on the spectrum of initial-state structure and of the final-state interaction and three-body correlations in Helium isotope He-10. It discusses three-body-correlation that clarify the role of the final-state interaction in the study. It concludes that the ground state peak observed in the spectrum of He-10 populated in reactions with Lithium isotope Li-11 is expected to be a superposition of 1-, 0+, and 2+ states.

The article discusses the process of anomalous population of 10He in the proton knockout reaction with a 11Li beam. Topics discussed include the model that aims for sudden removal of a proton from 11Li beam from populating a threebody 10He, superposition of different states in 10He, and 10He production in reaction with 14Be.

The article focuses on a study to compares the effects on spectrum of initial-state structure, final-state interaction and three-body correlations in Helium isotope (He) 10He. It discusses three-body-correlation that clarify the role of the final-state interaction in the study. It also concludes that the ground state peak observed in the spectrum of He populated in reactions with Lithium isotope (Li) 11Li expected to be a superposition of 1-, 0+, and 2+ states.

The article presents a study that investigates the presence of a structure with the lowest energy observed in the 10Helium (He) spectrum populated in the proton knockout reaction with a 11Lithium (Li) beam. Topics include a ground state peak in helium isotope spectrum that indicates halo size of lithium isotope, three-body-correlation studies that clarify role of the final-state interaction, and 10He in a alpha knockout from 14Beryllium (Be).

The article presents a study focusing on anomalous population of helium (He) states in reactions with lithium (Li). The results of the study include groundstate peak in the spectrum of He populated in reactions with Li, calculation results similar to those of the experimental results obtained in the knockout reactions of halo system, and the importance of the theoretical studies in finding of complex and unusual phenomena in the exotic dripline systems.

The first excited, Jπ = 2+ state of 16Ne at E* = 1.69(2) MeV is well populated in neutron knockout reactions with a 17Ne beam and the correlations between the momenta of the three final fragments following 2p decay were measured. The correlation pattern showed aspects of both sequential and diprotonlike decay, which were reproduced in three-body 14O + P + P calculations. These calculations suggest that interference between these processes is responsible for the observed features which can be described in terms of a "tethered decay mechanism." The intrinsic width of this state was constrained to be from 100 to 250 keV. Higher excited states populating the 13N + P + P + P exit channel were found at E* = 8.37(10) and 10.76(20) MeV. [ABSTRACT FROM AUTHOR]