Marius Mirea - Academia.edu (original) (raw)

Papers by Marius Mirea

Europhysics Letters (EPL), 1997

ABSTRACT

Physics Procedia, 2012

In this presentation, a generalization of the time dependent pairing equations is presented by in... more In this presentation, a generalization of the time dependent pairing equations is presented by including the Landau-Zener effect in the superfluid model. These new equations allows a mixing of seniority one configurations that allows us to obtain a ground state at the end of the process. An application concerning the C-14 emission is offered and its fine structure is explained. These new equations are furthermore used to evidence a dynamical pair breaking effect that could explain the fine odd-even effect in cold fission. The partition of the dissipated energy between the two fission fragments will be also modeled. Finally, the time dependent pairing equations are used to deduce a model for non-adiabatic cranking inertia.

Physics Procedia, 2013

The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the tim... more The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the other separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234 U parent nucleus.

Physics Procedia, 2012

In this presentation, a generalization of the time dependent pairing equations is presented by in... more In this presentation, a generalization of the time dependent pairing equations is presented by including the Landau-Zener effect in the superfluid model. These new equations allows a mixing of seniority one configurations that allows us to obtain a ground state at the end of the process. An application concerning the C-14 emission is offered and its fine structure is explained. These new equations are furthermore used to evidence a dynamical pair breaking effect that could explain the fine odd-even effect in cold fission. The partition of the dissipated energy between the two fission fragments will be also modeled. Finally, the time dependent pairing equations are used to deduce a model for non-adiabatic cranking inertia.

Physics Procedia, 2013

The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the tim... more The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the other separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234 U parent nucleus.

The European Physical Journal A, 2014

ABSTRACT Correlations between the potential energy surface structure and the mass distributions o... more ABSTRACT Correlations between the potential energy surface structure and the mass distributions observed in the production of superheavy nuclei are evidenced. The isomeric states are identified by spanning the multidimensional configuration space from the contact point of the colliding nuclei up to the formation of the compound nucleus. The available degrees of freedom are the elongation, the necking, the mass asymmetry, and the deformations of the two colliding nuclei. Using the macroscopic-microscopic model based on the Woods-Saxon two-center shell model, several minima in the potential energy landscape were revealed. The fission process from these isomeric states was investigated and the probabilities of realization of possible partitions were calculated in the WKB approximation. The inertia was computed in the framework of the cranking model. The identified correlations indicate that the mass distribution attributed to quasifission in previous studies can be alternatively explained as a cold-fission process from excited states.

Physical Review C, 2008

When the time dependent Hartree-Fock-Bogoliubov intrinsic equations of motion are solved in the c... more When the time dependent Hartree-Fock-Bogoliubov intrinsic equations of motion are solved in the case of seniority one nuclear systems, the unpaired nucleon remains on the same orbital. The blocking effect hinders the possibility to skip from one orbital to another. This unpleasant feature is by-passed with a new set of pairing time dependent equations that allows the possibility that the unpaired nucleon changes its single-particle level. These equations generalize the time dependent Hartree-Fock-Bogoliubov equations of motion by including the Landau-Zener effect. The derivation of these new equations is presented in details. These equations are applied in the case of a superasymmetric fission process, that is, in order to explain the fine structure the 14 C emission from 233 Ra. A new version of the Woods-Saxon model extended for two-center potentials is used in this context. PACS numbers: 24.10.Eq Coupled channel and distorted wave model; 23.70.+j Heavy-particle decay

Physical Review C, 1998

ABSTRACT

Physical Review C, 1996

ABSTRACT

Physical Review C, 2007

The structures observed in the sub-threshold neutron-induced fission of 232 Th were investigated ... more The structures observed in the sub-threshold neutron-induced fission of 232 Th were investigated employing a recent developed model. Theoretical singleparticle excitations of a phenomenological two-humped barrier are determined by solving a system of coupled differential equations for the motion along the optimal fission path. A rather good agreement with experimental data was obtained using a small number of independent parameters. It is predicted that the structure at 1.4 and 1.6 MeV is mainly dominated by spin 3/2 partial cross-section with small admixture of spin 1/2, while the structure at 1.7 MeV is given by a large partial cross section of spin 5/2. PACS numbers: 24.75.+i,25.85.Ec Threshold Resonant Structure of the 232 Th Neutron-Induced Fission Cross Section

Physical Review C, 2014

The time dependent equations of motion for the pair breaking effect were corroborated with a cond... more The time dependent equations of motion for the pair breaking effect were corroborated with a condition that fixes dynamically the number of particles on the two fission fragment. The single particle level scheme was calculated with the Woods-Saxon superasymmetric two center shell model. This model provides a continuous variation of the energies from one nucleus up to two separated fragments. The dissipated energy resorts from the time dependent pairing equations. A peculiar phenomenon was observed experimentally in cold fission: the odd partition yields are favored over the even ones. This odd-even effect for cold fission was explained microscopically.

Physical Review C, 2010

We investigate the cold fission of 252 Cf within the two center shell model to compute the potent... more We investigate the cold fission of 252 Cf within the two center shell model to compute the potential energy surface. The fission yields are estimated by using the semiclassical penetration approach. It turns out that the inner cold valley of the total potential energy is strongly connected with Z=50 magic number. The agreement with experimental values is very much improved only by considering mass and charge asymmetry degrees of freedom. Thus, indeed cold fission of 252 Cf is a Sn-like radioactivity, related the other two "magic radioactivities", namely α-decay and heavycluster decay, called also Pb-like radioactivity. This calculation provides the necessary theoretical confidence to estimate the penetration cross section in producing superheavy nuclei, by using the inverse fusion process.

Physical Review C, 2011

The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the tim... more The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the another separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The fission path is obtained in the frame of the macroscopic-microscopic model. The single particle level schemes are obtained within the two center Woods-Saxon shell model. It is shown that the available intrinsic dissipated energy is not shared proportionally to the masses of the two fission fragments. If the heavy fragment possesses nucleon numbers close to the magic ones, the accumulated intrinsic excitation energy is lower than that of the light fragment.

Physical Review C, 2001

Using an α decay level scheme, the fine structure in odd nuclei is explained by taking into accou... more Using an α decay level scheme, the fine structure in odd nuclei is explained by taking into account the radial and rotational couplings between the unpaired valence nucleon and the core of the decaying system. It is shown that the experimental behavior of the α decay fine structure phenomenon is governed by the dynamical characteristics of the system.

Nuclear Physics A, 2006

An improved version of the two-center shell model based on a double harmonic potential is describ... more An improved version of the two-center shell model based on a double harmonic potential is described. More realistic dependencies of the generalized angular momentum operators associated with the nuclear shape parameterization are determined and presented in detail. The amelioration produced by this better description is underlined by quantifying the effects on the potential energy surface in the fission processes. For this purpose, a nuclear shape parameterization characterized by the most important macroscopic degrees of freedom, namely elongation, necking-in and mass asymmetry, is used. The mathematical details are presented together with the solvable matrix elements.

Modern Physics Letters A, 2003

The Landau-Zener effect is generalized for many-body systems with pairing residual interactions. ... more The Landau-Zener effect is generalized for many-body systems with pairing residual interactions. The microscopic equations of motion are obtained and the 14 C decay of 223 Ra spectroscopic factors are deduced. An asymmetric nuclear shape parametrization given by two intersected spheres is used. The single particle level scheme is determined in the frame of the superasymmetric two-center shell. The deformation energy is computed in the microscopic-macroscopic approximation. The penetrabilities are obtained within the WKB approximation. The fine structure of the cluster decay analyzed in the frame of this formalism gives a very good agreement with the experimental ratio of partial half-lives obtained in special conditions. *

EPL (Europhysics Letters), 2013

ABSTRACT A two-center shell model provides the possibility to characterize precisely scission con... more ABSTRACT A two-center shell model provides the possibility to characterize precisely scission configurations. Therefore, low-energy disintegration processes could be described within such models. A Woods-Saxon two-center shell model, recently elaborated, was used to investigate the cluster decay, the low-energy fission and the synthesis of superheavy elements. In the following, the model is applied to the alpha-decay of superheavy elements as superasymmetric fission.

EPL (Europhysics Letters), 2009

ABSTRACT We investigate the cold fission/fusion paths of superheavy nuclei within the two-center ... more ABSTRACT We investigate the cold fission/fusion paths of superheavy nuclei within the two-center shell model, in order to find the best projectile-target combinations of their production. The fission/fusion yields are estimated by using the semiclassical approach. We predict several asymmetric combinations of relative long-living fragments, which can be used in fusion experiments of superheavy nuclei with Z>118.

Europhysics Letters (EPL), 1997

ABSTRACT

Physics Procedia, 2012

In this presentation, a generalization of the time dependent pairing equations is presented by in... more In this presentation, a generalization of the time dependent pairing equations is presented by including the Landau-Zener effect in the superfluid model. These new equations allows a mixing of seniority one configurations that allows us to obtain a ground state at the end of the process. An application concerning the C-14 emission is offered and its fine structure is explained. These new equations are furthermore used to evidence a dynamical pair breaking effect that could explain the fine odd-even effect in cold fission. The partition of the dissipated energy between the two fission fragments will be also modeled. Finally, the time dependent pairing equations are used to deduce a model for non-adiabatic cranking inertia.

Physics Procedia, 2013

The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the tim... more The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the other separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234 U parent nucleus.

Physics Procedia, 2012

In this presentation, a generalization of the time dependent pairing equations is presented by in... more In this presentation, a generalization of the time dependent pairing equations is presented by including the Landau-Zener effect in the superfluid model. These new equations allows a mixing of seniority one configurations that allows us to obtain a ground state at the end of the process. An application concerning the C-14 emission is offered and its fine structure is explained. These new equations are furthermore used to evidence a dynamical pair breaking effect that could explain the fine odd-even effect in cold fission. The partition of the dissipated energy between the two fission fragments will be also modeled. Finally, the time dependent pairing equations are used to deduce a model for non-adiabatic cranking inertia.

Physics Procedia, 2013

The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the tim... more The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time-dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the other separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The excitation energy in a wide distribution of fission fragments is calculated for the 234 U parent nucleus.

The European Physical Journal A, 2014

ABSTRACT Correlations between the potential energy surface structure and the mass distributions o... more ABSTRACT Correlations between the potential energy surface structure and the mass distributions observed in the production of superheavy nuclei are evidenced. The isomeric states are identified by spanning the multidimensional configuration space from the contact point of the colliding nuclei up to the formation of the compound nucleus. The available degrees of freedom are the elongation, the necking, the mass asymmetry, and the deformations of the two colliding nuclei. Using the macroscopic-microscopic model based on the Woods-Saxon two-center shell model, several minima in the potential energy landscape were revealed. The fission process from these isomeric states was investigated and the probabilities of realization of possible partitions were calculated in the WKB approximation. The inertia was computed in the framework of the cranking model. The identified correlations indicate that the mass distribution attributed to quasifission in previous studies can be alternatively explained as a cold-fission process from excited states.

Physical Review C, 2008

When the time dependent Hartree-Fock-Bogoliubov intrinsic equations of motion are solved in the c... more When the time dependent Hartree-Fock-Bogoliubov intrinsic equations of motion are solved in the case of seniority one nuclear systems, the unpaired nucleon remains on the same orbital. The blocking effect hinders the possibility to skip from one orbital to another. This unpleasant feature is by-passed with a new set of pairing time dependent equations that allows the possibility that the unpaired nucleon changes its single-particle level. These equations generalize the time dependent Hartree-Fock-Bogoliubov equations of motion by including the Landau-Zener effect. The derivation of these new equations is presented in details. These equations are applied in the case of a superasymmetric fission process, that is, in order to explain the fine structure the 14 C emission from 233 Ra. A new version of the Woods-Saxon model extended for two-center potentials is used in this context. PACS numbers: 24.10.Eq Coupled channel and distorted wave model; 23.70.+j Heavy-particle decay

Physical Review C, 1998

ABSTRACT

Physical Review C, 1996

ABSTRACT

Physical Review C, 2007

The structures observed in the sub-threshold neutron-induced fission of 232 Th were investigated ... more The structures observed in the sub-threshold neutron-induced fission of 232 Th were investigated employing a recent developed model. Theoretical singleparticle excitations of a phenomenological two-humped barrier are determined by solving a system of coupled differential equations for the motion along the optimal fission path. A rather good agreement with experimental data was obtained using a small number of independent parameters. It is predicted that the structure at 1.4 and 1.6 MeV is mainly dominated by spin 3/2 partial cross-section with small admixture of spin 1/2, while the structure at 1.7 MeV is given by a large partial cross section of spin 5/2. PACS numbers: 24.75.+i,25.85.Ec Threshold Resonant Structure of the 232 Th Neutron-Induced Fission Cross Section

Physical Review C, 2014

The time dependent equations of motion for the pair breaking effect were corroborated with a cond... more The time dependent equations of motion for the pair breaking effect were corroborated with a condition that fixes dynamically the number of particles on the two fission fragment. The single particle level scheme was calculated with the Woods-Saxon superasymmetric two center shell model. This model provides a continuous variation of the energies from one nucleus up to two separated fragments. The dissipated energy resorts from the time dependent pairing equations. A peculiar phenomenon was observed experimentally in cold fission: the odd partition yields are favored over the even ones. This odd-even effect for cold fission was explained microscopically.

Physical Review C, 2010

We investigate the cold fission of 252 Cf within the two center shell model to compute the potent... more We investigate the cold fission of 252 Cf within the two center shell model to compute the potential energy surface. The fission yields are estimated by using the semiclassical penetration approach. It turns out that the inner cold valley of the total potential energy is strongly connected with Z=50 magic number. The agreement with experimental values is very much improved only by considering mass and charge asymmetry degrees of freedom. Thus, indeed cold fission of 252 Cf is a Sn-like radioactivity, related the other two "magic radioactivities", namely α-decay and heavycluster decay, called also Pb-like radioactivity. This calculation provides the necessary theoretical confidence to estimate the penetration cross section in producing superheavy nuclei, by using the inverse fusion process.

Physical Review C, 2011

The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the tim... more The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the another separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The fission path is obtained in the frame of the macroscopic-microscopic model. The single particle level schemes are obtained within the two center Woods-Saxon shell model. It is shown that the available intrinsic dissipated energy is not shared proportionally to the masses of the two fission fragments. If the heavy fragment possesses nucleon numbers close to the magic ones, the accumulated intrinsic excitation energy is lower than that of the light fragment.

Physical Review C, 2001

Using an α decay level scheme, the fine structure in odd nuclei is explained by taking into accou... more Using an α decay level scheme, the fine structure in odd nuclei is explained by taking into account the radial and rotational couplings between the unpaired valence nucleon and the core of the decaying system. It is shown that the experimental behavior of the α decay fine structure phenomenon is governed by the dynamical characteristics of the system.

Nuclear Physics A, 2006

An improved version of the two-center shell model based on a double harmonic potential is describ... more An improved version of the two-center shell model based on a double harmonic potential is described. More realistic dependencies of the generalized angular momentum operators associated with the nuclear shape parameterization are determined and presented in detail. The amelioration produced by this better description is underlined by quantifying the effects on the potential energy surface in the fission processes. For this purpose, a nuclear shape parameterization characterized by the most important macroscopic degrees of freedom, namely elongation, necking-in and mass asymmetry, is used. The mathematical details are presented together with the solvable matrix elements.

Modern Physics Letters A, 2003

The Landau-Zener effect is generalized for many-body systems with pairing residual interactions. ... more The Landau-Zener effect is generalized for many-body systems with pairing residual interactions. The microscopic equations of motion are obtained and the 14 C decay of 223 Ra spectroscopic factors are deduced. An asymmetric nuclear shape parametrization given by two intersected spheres is used. The single particle level scheme is determined in the frame of the superasymmetric two-center shell. The deformation energy is computed in the microscopic-macroscopic approximation. The penetrabilities are obtained within the WKB approximation. The fine structure of the cluster decay analyzed in the frame of this formalism gives a very good agreement with the experimental ratio of partial half-lives obtained in special conditions. *

EPL (Europhysics Letters), 2013

ABSTRACT A two-center shell model provides the possibility to characterize precisely scission con... more ABSTRACT A two-center shell model provides the possibility to characterize precisely scission configurations. Therefore, low-energy disintegration processes could be described within such models. A Woods-Saxon two-center shell model, recently elaborated, was used to investigate the cluster decay, the low-energy fission and the synthesis of superheavy elements. In the following, the model is applied to the alpha-decay of superheavy elements as superasymmetric fission.

EPL (Europhysics Letters), 2009

ABSTRACT We investigate the cold fission/fusion paths of superheavy nuclei within the two-center ... more ABSTRACT We investigate the cold fission/fusion paths of superheavy nuclei within the two-center shell model, in order to find the best projectile-target combinations of their production. The fission/fusion yields are estimated by using the semiclassical approach. We predict several asymmetric combinations of relative long-living fragments, which can be used in fusion experiments of superheavy nuclei with Z>118.