arXiv subjects

C. M. Raduta

Publications and source records attributed to C. M. Raduta.

21 records · Page 2Linked to original sources

arXiv2005

New features of some proton-neutron collective states

Using a schematic solvable many-body Hamiltonian, one studies a new type of proton-neutron excitations within a time dependent variational approach. Classical equations of motion are linearized and subsequently solved analytically. The harmonic state energy is compared with the energy of the first excited state provided by diagonalization as well as with the energies obtained by a renormalized RPA and a boson expansion procedure. The new collective mode describes a wobbling motion, in the space of isospin, and collapses for a particle-particle interaction strength which is much larger than the physical value. A suggestion for the description of the system in the second nuclear phase is made. We identified the transition operators which might excite the new mode from the ground state.

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arXiv2005

New results for the fully renormalized proton-neutron quasiparticle random phase approximation

A many-body Hamiltonian describing a system of Z protons and N neutrons moving in spherical shell model mean field and interacting among themselves through proton-proton and neutron-neutron pairing and a dipole-dipole proton-neutron interaction of both particle-hole and particle-particle type, is treated within a fully renormalized (FR) pnQRPA approach. Two decoupling schemes are formulated. One of them decouples the equations of motion of particle total number conserving and non-conserving operators. One ends up with two very simple dispersion equations for phonon operators which are formally of Tamm-Dancoff types. For excitations in the (N-1,Z+1) system, Ikeda sum rule is fully satisfied provided the BCS equations are renormalized as well and therefore solved at a time with the FRpnQRPA equations. Next, one constructs two operators ${\cal R}^{\dagger}_{1μ}$, ${\cal R}_{1,-μ}(-)^{1-μ}$ which commutes with the particle total number conserving operators, ${\cal A}^{\dagger}_{1μ}$ and ${\cal A}_{1,-μ}(-)^{1-μ}$, and moreover could be renormalized so that they become bosons. Then, a phonon operator is built up as a linear combination of these four operators. The FRpnQRPA equations are written down for this complex phonon operator and the ISR is calculated analytically. This formalism allows for an unified description of the dipole excitations in four neighboring nuclei (N-1,Z+1),(N+1,Z-1),(N-1,Z-1),(N+1,Z+1). The phonon vacuum describes the (N,Z) system ground state.

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arXiv2004

Description of the two neutrino double beta decay in deformed nuclei with projected spherical single particle states

Using an angular momentum projected single particle basis, a pnQRPA approach is used to study the $2νββ$ properties of ten isotopes, exhibiting various quadrupole deformations. The mother and daughter nuclei exhibit different quadrupole deformations. Since the projected basis enables a unified description of deformed and spherical nuclei, situations where the nuclei involved in the double beta decay process are both spherical, both deformed or one spherical and another deformed, can be treated through a sole formalism. Dependence of single $β^-$ and $β^+$ strength distribution on atomic mass number and nuclear deformation is analyzed. For the double beta decay process, the Gamow-Teller transition amplitudes and half lives are calculated. Results are compared with the experimental data as well as with the predictions of other theoretical approaches. The agreement between the present results and experimental data is fairly good.

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