As was shown in our previous work [1], the beta spectrum of unique first forbidden decays is sensitive to beta-neutrino correlation. As a test case, we decided to measure the decay of 16N, which has a spin parity of 2−. 28% of the time, it decays to the 0+ ground state of 16O with Q-value of 10.4 MeV. Other branches of the decay are pure GT decays to 1− and 3− with Q-values 3.3 and 4.1 MeV,...
A new theoretical approach for alpha correlation in nuclei is investigated in term of the hyper-Pfaffian [1]. The Pfaffian has been recently investigated to formulate the pairing correlation and is useful in investigating the sign-problem of Onishi formula [2], Wick’s theorem, and the variational Monte Carlo [3]. While the hyper-Pfaffian, which is an extension of the Pfaffian for...
Neutrinoless double beta decay is a rare and important process to know whether neutrinos are Dirac or Majorana particles. It also gives hints of absolute neutrino masses. But this weak process is still unobserved even after 70 years of its predictions [1]. Problem is in the uncertainties in theoretical calculations of nuclear matrix element(NME) which is directly related to the decay rate of...
Since the nuclear force is much stronger than the electromagnetic one, it mainly determines the properties of atomic nuclei. Nevertheless, in specific studies, it is important to evaluate the electromagnetic contribution to the properties of atomic nuclei. Since the electromagnetic force is well known in contrast to the nuclear force, its contribution to properties of atomic nuclei can be...
In previous studies dipole bands were observed in a number of even Hg isotopes, including 196Hg where one dipole band was found [1]. In an experiment at iThemba LABS we observed both this and a second dipole band in 196Hg and could make an unambiguous spin and parity assignments from DCO and polarization measurements.
The experiment was performed using the AFRODITE array that consisted of 7...
- Background: Magnetic dipole (M1) excitation is the leading mode of nuclear excitation by the magnetic field, which couples unnatural-parity states. As expected from the form of operator, this mode may provide the information on the spin-related properties, including dineutron and diproton correlations [1-4].
- Purpose: The M1 excitation of two valence nucleons with pairing correlation is...
Stellar helium burning results in the formation of carbon and oxygen [1]. However, the carbon-to-oxygen ratio at the end of helium burning is not well known, despite its importance in stellar evolution theory. Furthermore, alpha particle clustering in 12C remains somewhat mysterious, with the structure of the first excited 0+ Hoyle state still under question [2].
The gamma-ray beam facility...
In recent years experimental measurements and many theoretical investigations have been devoted to the decay and the structure of an excited 16O. The main aim of these researches has been the quest for signatures of α-cluster structures of the 16O at different excitation energies.
We have studied the decay of a 16O* Quasi projectile in 4 α-particles in the final state by the reaction...
The neutron-rich $^{144-146}$Ba isotopes have been studied recently in terms
of their experimental B(E3) values [1,2]. Although featuring large uncertainties,
the results were found to be significantly larger than any theoretical calculation.
Similar questions exist for the slightly lighter isotope $^{140}$Ba, which is particularly
interesting since it is located at the onset of octupole...
Information about the proton-neutron interaction can be obtained from nuclear states particularly sensitive to the proton-neutron degree of freedom, of which low-lying isovector states are representatives. The existence of a low-lying isovector octupole excitation in near-spherical nuclei, for which candidates were recently proposed, was tested. The assignment is based on strong M1 transitions...
The nuclear mass $\sim$ 130 is the most promising region in search of chiral symmetry. The two nearly degenerate ($\Delta$I = 1) bands, based on the particle configuration $\pi h_{11/2}\otimes\nu h_{11/2}$, are the initial evidence of chiral behavior in nuclei, as found in $^{126}$I [1]. The electromagnetic selection rules of inter-band and intra-band provide a tenacious proof of chiral bands....
Nowadays, a great amount of experimental effort is devoted to the study of the shell closures far from stability. One of the most studied case is the doubly-magic and self-conjugated 100Sn nucleus.
The spectroscopy properties of the tin isotopic chain, when approaching the 100Sn [1], have in particular been subject to intense study. Tin nuclei exhibit a seniority type of behavior [2] but the...
This work reports on the utilisation of gamma-ray coincidences between germanium and
cerium-doped lanthanum tri-bromide LaBr3:(Ce) scintillation detectors for the determination
of electromagnetic transition rates in the pico to nanosecond regime. The technique utilises
the high-quality full-energy peak resolution of the LaBr3(Ce) detectors coupled with their
excellent timing responses in order...
An enhancement of the B(E2, 2$^+_1\rightarrow$ 0$^+_1$) and unexpectedly low B(E2, 4$^+_1\rightarrow$ 2$^+_1$) values was found in $_{50}$Sn isotopes below mid-shell. However, the puzzling B(E2, 2$^+_1\rightarrow$ 0$^+_1$) systematics around N = 60 was understood very recently in state-of-the-art Monte-Carlo shell model calculations [1] by activating protons in the 1g9/2 orbit and a...
In the work presented here we have studied the mainly fusion-evaporation 56Fe(p,n)56Co reaction with an incident 10 MeV proton-beam. The gamma radiation emitted in the de-excitation of the excited odd-odd 56Co nucleus was measured in-beam with four high-purity germanium (Ge) MINIBALL-triple detectors. The MINIBALL array is a γ-ray spectrometer optimized to achieve a high photo-peak efficiency...
By using a non-relativistic independent particle approach, we have investigated the mechanism promoting $N=34$ as a new magic number [1]. We carried out Hartree-Fock plus Bardeen-Cooper Schrieffer and Quasi-particle Random Phase Approximation calculations by consistently using the same finite-range interaction in all the the steps of our approach [2]. We used four Gogny-like interactions, with...
This work is a continuation of our previous works devoted to studies of neutron-rich nuclei in the “north-east” of the 78Ni core. The main motivation of those studies is understanding structure of this very exotic nuclei. Large excess of neutrons modify shell structure compared to the structure close to stability line. It has been predicted by various calculations that large excess of neutrons...
Odd-odd nuclei are good candidates for probing shell structures away from the valley of stability. In general, odd-odd nuclei are difficult to study as they can have coexisting low-lying two-quasiparticle states (in contrast to even-even nuclei),i.e., in odd-odd nuclei, the energy differences between low-lying 2-qp states can be very small (less than 100 keV). Such small differences are...
The ground state properties of neutron deficient nuclei in the region from I to Bi with Z = 53 -83 and N = 56 -102 has been studied within the relativistic mean field formalism [B.D. Serot et al., Adv. Nucl. Phys. 16, 1 (1986); Y.K. Gambhir et al., Ann. Phys. 198, 132 (1990)] with NL3, DDME-1, DDME-2 parameterizations, with deformed consideration of nuclei. The calculated binding energies are...
The increase of energy of the ISOLDE radioactive beams made possible through the HIE-ISOLDE project has opened new possibilities for reactions studies with exotic beams. A particular challenge is presented by the light nuclei where unbound final states play an important role and the role of the continuum is by now known to be important. Theoretical work on the reaction mechanisms involved...
Deformed nuclei with non-axial shape show variety of interesting structures. Most recently a new mode of excitation, transverse wobbling, was suggested to occur in odd-mass triaxial nuclei [1]. Following that the excited h11/2 band in 135Pr was interpreted as excibition of such wobbling [1,2]. However, several questions on such a mode remain open, in particular the freezing of the proton...
Shape coexistence is a characteristic phenomenon of finite many-body quantum systems where different nuclear shapes coexist within the typical energy range of nuclear excitations.
The principle behind this phenomenon is the contrast between two different tendencies: on one hand valence nucleons and np-nh excitations driving the nucleus to collective configurations; on the other hand, pair...
The 19F(p,$\alpha$)16O reaction has a twofold importance: it allows to investigate the spectroscopy of low angular momentum high-energy states in the self-conjugate 20Ne compound nucleus and, at low energy, it is involved in astrophysical models aiming at describing the fluorine nucleosynthesis in stars.
Despite its importance, fragmentary (and often contrasting) experimental data on its...
Spin-tensor decomposition (STD) is a useful tool to retrieve the basic two-body structure (central, spin-orbit and tensor force) of model-space dependent shell model effective interactions [1]. For last one and half decades, it has been used with the aim to understand the contribution of central, spin-orbit and tensor force to the angular momentum average two-body component called monopole...
A study of continuum excitation was performed by using as a tool the breakup of light projectiles on a target in inverse kinematics. In this context a complete study of the $^6$Li+p and $^7$Li+p systems was pursued by measuring not only the breakup but also elastic scattering and other reaction channels with significant probability under the same experimental conditions. The relevant...
In the present work, we have studied the excitation functions (EFs) of 260Sg, formed in fusion reactions 51V+209Bi [1] and 52Cr+208Pb [2] 208Pb at energies E = 20-26 MeV, based on Dynamical Cluster-decay Model (DCM) [3,4], to use some other nuclear interaction potentials derived from Skyrme energy density functional (SEDF) based on semi-classical extended Thomas Fermi (ETF) approach. Wew...
Since its discovery, fission appeared as a complex process where different nuclear properties interplay shaping the characteristics of the emerging fission fragment distributions. In general, the influence of the shell effects is expected to decrease with increasing excitation energy of the fissioning nucleus, making the process driven by almost pure liquid-drop properties. Recently, some...
The production of neutron-rich heavy nuclei in the vicinity of N = 126 shell closure has received a boost of interest recently, since the properties of these nuclei are fundamental for the understanding of the actual path of r-process and synthesis of the heavy elements. The nuclear structure studies in the region close to the double magic $^{208}$Pb nucleus, where benchmark cases are...
In this work, the $^3{\rm H}(\alpha, \gamma)^7{\rm Li}$ and $^3{\rm He}(\alpha, \gamma)^7{\rm Be}$ mirror radiative capture reactions that are of interest to nuclear astrophysics are considered from the microscopic viewpoint within the multiscale algebraic version of the resonating group model [1]. The total and partial astrophysical $S$ factors for these reactions as well as the nuclear phase...
The $\beta$-decay properties are very important for understanding the nuclear structure evolution at extreme N/Z ratios, for analysis of radioactive ion-beam experiments, and modeling of the astrophysical r-process. For this reason, the $\beta$-decay properties of r-process “waiting-point nuclei” $^{129}$Ag, $^{130}$Cd, and $^{131}$In provides valuable information, with important tests of...
