Search

Mechanism of simultaneous non-sequential four-neutron (4n) emission (or "true" 4n-decay) has been considered in phenomenological five-body approach. This approach is analogous to the model of the direct decay to the continuum often applied to 2n- and 2p-decays. It is demonstrated that 4n-decay fragments should have specific energy and angular correlations reflecting strong spatial correlations of "valence" nucleons orbiting in their 4n-precursors. Due to the Pauli exclusion principle, the valence neutrons are pushed to the symmetry-allowed configurations in the 4n-precursor structure, which causes a "Pauli focusing" effect. Prospects of the observation of the Pauli focusing have been considered for the 4n-precursors 7H and 28O. Fingerprints of their nuclear structure or/and decay dynamics are predicted. [ABSTRACT FROM AUTHOR]

One of the major problems in numerical solution of coupled differential equations is the maintenance of linear independence for different sets of solution vectors. A novel method for solution of radial Schrödinger equations is suggested. It consists of rearrangement of coupled equations in a way that is appropriate to avoid usual numerical instabilities associated with components of the wave function in their classically forbidden regions. Applications of the new method for nuclear structure calculations within the hyperspherical harmonics approach are given. [ABSTRACT FROM AUTHOR]

The unknown isotope 26S, expected to decay by two-proton (2p) emission, was studied theoretically and searched experimentally. The structure of this nucleus was examined within the relativistic mean field (RMF) approach. A method for taking into account the many-body structure in the three-body decay calculations was developed. The results of the RMF calculations were used as an input for the three-cluster decay model optimized for the study of a possible 2p decay branch of this nucleus. The experimental search for 26S was performed by fragmentation of a 50.3 A MeV 32S beam. No events of a particle-stable 26S or 25P (a presumably proton-unstable subsystem of 26S) were observed. Based on the obtained production systematics, an upper half-life limit of T1/2<79 ns was established from the time-of-flight through the fragment separator. Together with the theoretical lifetime estimates for two-proton decay, this gives a decay energy limit of Q2p>640 keV for 26S. Analogous limits for 25P are found as T1/2 < 38 ns and Qp>110keV. In the case that the one-proton emission is the main branch of the 26S decay, a limit Q2p>230 keV would follow for this nucleus. According to these limits, it is likely that 26S resides in the picosecond lifetime range. [ABSTRACT FROM AUTHOR]

Nowadays quantum-mechanical three-cluster theory allows one to reliably calculate the processes of 2p radioactivity (true three-body decays) and the corresponding energy and angular correlations. However, the connection of the three-cluster final state configuration with possibly manybody internal structure of the nucleus is unclear in this approach. A simple method for taking into account the many-body structure in the three-body decay calculations was developed. The results of the relativistic mean field (RMF) calculations are used as an input for the three-cluster decay model. The calculations for the prospective two-proton emitter 26S are provided. [ABSTRACT FROM AUTHOR]

A modified variable phase method for the numerical solution of coupled radial Schrödinger equations, which maintains linear independence for different sets of solution vectors, is suggested. The modification involves rearrangement of coupled equations to avoid the usual numerical instabilities associated with components of the wave function in their classically forbidden regions. The modified method is applied to nuclear structure calculations of halo nuclei within the hyperspherical harmonics approach. [ABSTRACT FROM AUTHOR]

An unusually large value of the 22C matter radius, extracted by Tanaka et al. [Phys. Rev. Lett. 104, 062701 (2010)] from measured reaction cross sections, attracted great attention of scientific community. Since that time, several experimental works related to the 22C nucleus have appeared in the literature. Some of the experimental data, measured with high accuracy, allow us to fix 22C structure more reliably. Two limiting models reproducing 22C nuclear structure within the three-body cluster approach, that allow us to describe all existing experimental data, are presented. The 22C ground state, continuum structure, and geometry are obtained. With fixed 22C wave function, the prediction for the soft dipole mode in 22C, which is studied in the process of Coulomb fragmentation, is performed. [ABSTRACT FROM AUTHOR]