Julian Srebrny - Academia.edu (original) (raw)

Papers by Julian Srebrny

Physical Review C, 2015

Background: The chain of Sm isotopes exhibits a wide range of nuclear shapes and collective behav... more Background: The chain of Sm isotopes exhibits a wide range of nuclear shapes and collective behavior. While the onset of deformation for N > 82 has been well studied both experimentally and theoretically, fundamental data is lacking for some Sm isotopes with N < 82. Purpose: Electromagnetic transition rates represent a sensitive test of theoretical nuclear structure models. Lifetime measurements are furthermore complementary to Coulomb excitation experiments, and the two methods together can give access to spectroscopic quadrupole moments. Method: The lifetime of the 2 + 1 state in 140 Sm was measured with the recoil-distance Doppler shift technique using the reaction 124 Te(20 Ne, 4n) 140 Sm at 82 MeV. Theoretical calculations were performed based on a mapped collective Hamiltonian in five quadrupole coordinates (5DCH) and the Gogny D1S interaction. Results: The lifetime of the 2 + 1 state in 140 Sm was found to be 9.1(6) ps, corresponding to a B(E2; 2 + 1 → 0 + 1) value of 51(4) Weisskopf units. The theoretical calculations are in very good agreement with the experimental result. Conclusions: The B(E2; 2 + 1 → 0 + 1) value for 140 Sm fits smoothly into the systematic trend for the chain of Sm isotopes. The new beyond-mean field calculations are able to correctly describe the onset of collectivity in the Sm isotopes below the N = 82 shell closure for the first time.

Physical Review C, 2018

A Coulomb-excitation experiment to study electromagnetic properties of 42 Ca was performed using ... more A Coulomb-excitation experiment to study electromagnetic properties of 42 Ca was performed using 170 MeV calcium beam from TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. Gamma rays from excited states in 42 Ca were measured with the AGATA spectrometer. The magnitudes and relative signs of 10 E2 matrix elements coupling 6 low-lying states in 42 Ca, including the diagonal E2 matrix elements of 2 + 1 and 2 + 2 states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analysed using Quadrupole Sum Rule method and yielded overall quadrupole deformation parameters for 0 + 1,2 and 2 + 1,2 states, as well as asymmetry parameters for 0 + 1,2 states, establishing the coexistence of a weakly-deformed groundstate band and highly-deformed slightly triaxial side band in 42 Ca. The experimental results were compared with the state-of-the-art large-scale shell model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in 42 Ca.

Physical Review C, 2009

The development of deformation and shape coexistence in the vicinity of doubly magic 48 Ca, relat... more The development of deformation and shape coexistence in the vicinity of doubly magic 48 Ca, related to the weakening of the N = 28 shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive 44 Ar beam from the SPIRAL facility at GANIL. The 2 + 1 and 2 + 2 states in 44 Ar were excited on 208 Pb and 109 Ag targets at two different beam energies. B(E2) values between all observed states and the spectroscopic quadrupole moment of the 2 + 1 state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the 44 Ar nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic 48 Ca. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for 44 Ar and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the N = 28 shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

AIP Conference Proceedings

Physical Review C

ABSTRACT

International Journal of Modern Physics E

Lifetimes of the h 11/2 decoupled band in 131 La and supposed chiral bands in odd-odd 132 La have... more Lifetimes of the h 11/2 decoupled band in 131 La and supposed chiral bands in odd-odd 132 La have been measured using the Doppler Shift Atenuation method. The properties of all bands have been calculated in terms of the Core Quasi Particle Coupling and Core Particle Hole Coupling models by using in both cases the same phenomenological core of 130 Ba . A new band in 132 La has been found.

Acta Physica Polonica Series B

The lifetime of levels in the yrast band of 119I were measured by DSAM and RDM using the 109Ag (1... more The lifetime of levels in the yrast band of 119I were measured by DSAM and RDM using the 109Ag (13C,3n) reaction at E=54 MeV. The detailed description of data analysis including the stopping power determination and estimation of side feeding time is given. A modified method of RDM data analysis --- Recoil Distance Doppler Shape Attenuation (RDDSA) is used.

Acta Physica Polonica Series B

Lifetimes of the yrast states in 120Xe and ground state band below and above band crossing in 118... more Lifetimes of the yrast states in 120Xe and ground state band below and above band crossing in 118Te have been measured by DSAM in the 111Cd(12C,3n) reaction and by DSAM and RDM in the 109Ag(13C,p3n) reaction, respectively. The results are compared with E2 transition probabilities in 119I and 128Ba. The experimental data are compared with calculation done in the framework of the IBM1 model in the O(6) and SU(5) limits.

Acta Physica Polonica Series B

Lifetimes of 15 levels build on the π g9/2 hole state in the 119I nuclei have been measured. The ... more Lifetimes of 15 levels build on the π g9/2 hole state in the 119I nuclei have been measured. The Doppler Shift Attenuation and Recoil Distance Methods were used. Modified model of ``conflict coupling'', being an extension of ``shears mechanism'' model, reproduces experimental values of B(M1).

Lifetimes of 15 levels build on the pi g9/2 hole state in the 119I nuclei have been measured. The... more Lifetimes of 15 levels build on the pi g9/2 hole state in the 119I nuclei have been measured. The Doppler Shift Attenuation and Recoil Distance Methods were used. Modified model of ``conflict coupling'', being an extension of ``shears mechanism'' model, reproduces experimental values of B(M1).

The E2 and Ml intraband transition probabilities have been determined in 132La and 128Cs using th... more The E2 and Ml intraband transition probabilities have been determined in 132La and 128Cs using the Doppler Shift Attenuation method. The S(E2) and 5(M1) values suggest that 128Cs is a better candidate for the presence of chiral bands than 132La.

Eihgty-nine E2 matrix elements involving the lowest-lying states in 110Pd have been measured by C... more Eihgty-nine E2 matrix elements involving the lowest-lying states in 110Pd have been measured by Coulomb excitation and the recoil distance technique. The results from both experiments agree. This set of E2 matrix elemenets is sufficiently complete to allowed to use of non-energy weighted sum rules to project intrinsic frame E2 moments directly. These show coexistence of rotational bands with different, and sometimes large , deformations.

Acta Physica Polonica Series B

The role of pairing collective degrees of freedom is investigated within microscopic approach bas... more The role of pairing collective degrees of freedom is investigated within microscopic approach based on the general collective Bohr model which includes the effect of coupling with the pairing vibrations. The excitation energies observed in transitional Gd and Er isotopes are reproduced in the frame of the calculation containing no free parameters.

Acta Physica Polonica Series B

The quadrupole excitations of transuranic nuclei are described dynamically in the frame of the mi... more The quadrupole excitations of transuranic nuclei are described dynamically in the frame of the microscopic collective Bohr Hamiltonian modified by adding the coupling with the pairing vibrations. The ground-state bands in No and Fm even--even isotopes are reproduced within the model containing no adjustable parameters.

Acta Physica Polonica B, 2015

Acta Physica Polonica B, 2015

The spontaneous chiral symmetry breaking was experimentally studied at the Heavy Ion Laboratory o... more The spontaneous chiral symmetry breaking was experimentally studied at the Heavy Ion Laboratory of the University of Warsaw by use of the DSAM and DCO analysis. Obtained lifetimes, branching ratios and E2/M1 mixing ratios were used to determine B(M1) and B(E2) values. The preliminary results for 124 Cs confirm spontaneous chiral symmetry breaking hypothesis in the 15-20 spin range.

Physical Review C, 2015

Background: The chain of Sm isotopes exhibits a wide range of nuclear shapes and collective behav... more Background: The chain of Sm isotopes exhibits a wide range of nuclear shapes and collective behavior. While the onset of deformation for N > 82 has been well studied both experimentally and theoretically, fundamental data is lacking for some Sm isotopes with N < 82. Purpose: Electromagnetic transition rates represent a sensitive test of theoretical nuclear structure models. Lifetime measurements are furthermore complementary to Coulomb excitation experiments, and the two methods together can give access to spectroscopic quadrupole moments. Method: The lifetime of the 2 + 1 state in 140 Sm was measured with the recoil-distance Doppler shift technique using the reaction 124 Te(20 Ne, 4n) 140 Sm at 82 MeV. Theoretical calculations were performed based on a mapped collective Hamiltonian in five quadrupole coordinates (5DCH) and the Gogny D1S interaction. Results: The lifetime of the 2 + 1 state in 140 Sm was found to be 9.1(6) ps, corresponding to a B(E2; 2 + 1 → 0 + 1) value of 51(4) Weisskopf units. The theoretical calculations are in very good agreement with the experimental result. Conclusions: The B(E2; 2 + 1 → 0 + 1) value for 140 Sm fits smoothly into the systematic trend for the chain of Sm isotopes. The new beyond-mean field calculations are able to correctly describe the onset of collectivity in the Sm isotopes below the N = 82 shell closure for the first time.

Physical Review C, 2018

A Coulomb-excitation experiment to study electromagnetic properties of 42 Ca was performed using ... more A Coulomb-excitation experiment to study electromagnetic properties of 42 Ca was performed using 170 MeV calcium beam from TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. Gamma rays from excited states in 42 Ca were measured with the AGATA spectrometer. The magnitudes and relative signs of 10 E2 matrix elements coupling 6 low-lying states in 42 Ca, including the diagonal E2 matrix elements of 2 + 1 and 2 + 2 states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analysed using Quadrupole Sum Rule method and yielded overall quadrupole deformation parameters for 0 + 1,2 and 2 + 1,2 states, as well as asymmetry parameters for 0 + 1,2 states, establishing the coexistence of a weakly-deformed groundstate band and highly-deformed slightly triaxial side band in 42 Ca. The experimental results were compared with the state-of-the-art large-scale shell model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in 42 Ca.

Physical Review C, 2009

The development of deformation and shape coexistence in the vicinity of doubly magic 48 Ca, relat... more The development of deformation and shape coexistence in the vicinity of doubly magic 48 Ca, related to the weakening of the N = 28 shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive 44 Ar beam from the SPIRAL facility at GANIL. The 2 + 1 and 2 + 2 states in 44 Ar were excited on 208 Pb and 109 Ag targets at two different beam energies. B(E2) values between all observed states and the spectroscopic quadrupole moment of the 2 + 1 state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the 44 Ar nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic 48 Ca. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for 44 Ar and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the N = 28 shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

AIP Conference Proceedings

Physical Review C

ABSTRACT

International Journal of Modern Physics E

Lifetimes of the h 11/2 decoupled band in 131 La and supposed chiral bands in odd-odd 132 La have... more Lifetimes of the h 11/2 decoupled band in 131 La and supposed chiral bands in odd-odd 132 La have been measured using the Doppler Shift Atenuation method. The properties of all bands have been calculated in terms of the Core Quasi Particle Coupling and Core Particle Hole Coupling models by using in both cases the same phenomenological core of 130 Ba . A new band in 132 La has been found.

Acta Physica Polonica Series B

The lifetime of levels in the yrast band of 119I were measured by DSAM and RDM using the 109Ag (1... more The lifetime of levels in the yrast band of 119I were measured by DSAM and RDM using the 109Ag (13C,3n) reaction at E=54 MeV. The detailed description of data analysis including the stopping power determination and estimation of side feeding time is given. A modified method of RDM data analysis --- Recoil Distance Doppler Shape Attenuation (RDDSA) is used.

Acta Physica Polonica Series B

Lifetimes of the yrast states in 120Xe and ground state band below and above band crossing in 118... more Lifetimes of the yrast states in 120Xe and ground state band below and above band crossing in 118Te have been measured by DSAM in the 111Cd(12C,3n) reaction and by DSAM and RDM in the 109Ag(13C,p3n) reaction, respectively. The results are compared with E2 transition probabilities in 119I and 128Ba. The experimental data are compared with calculation done in the framework of the IBM1 model in the O(6) and SU(5) limits.

Acta Physica Polonica Series B

Lifetimes of 15 levels build on the π g9/2 hole state in the 119I nuclei have been measured. The ... more Lifetimes of 15 levels build on the π g9/2 hole state in the 119I nuclei have been measured. The Doppler Shift Attenuation and Recoil Distance Methods were used. Modified model of ``conflict coupling'', being an extension of ``shears mechanism'' model, reproduces experimental values of B(M1).

Lifetimes of 15 levels build on the pi g9/2 hole state in the 119I nuclei have been measured. The... more Lifetimes of 15 levels build on the pi g9/2 hole state in the 119I nuclei have been measured. The Doppler Shift Attenuation and Recoil Distance Methods were used. Modified model of ``conflict coupling'', being an extension of ``shears mechanism'' model, reproduces experimental values of B(M1).

The E2 and Ml intraband transition probabilities have been determined in 132La and 128Cs using th... more The E2 and Ml intraband transition probabilities have been determined in 132La and 128Cs using the Doppler Shift Attenuation method. The S(E2) and 5(M1) values suggest that 128Cs is a better candidate for the presence of chiral bands than 132La.

Eihgty-nine E2 matrix elements involving the lowest-lying states in 110Pd have been measured by C... more Eihgty-nine E2 matrix elements involving the lowest-lying states in 110Pd have been measured by Coulomb excitation and the recoil distance technique. The results from both experiments agree. This set of E2 matrix elemenets is sufficiently complete to allowed to use of non-energy weighted sum rules to project intrinsic frame E2 moments directly. These show coexistence of rotational bands with different, and sometimes large , deformations.

Acta Physica Polonica Series B

The role of pairing collective degrees of freedom is investigated within microscopic approach bas... more The role of pairing collective degrees of freedom is investigated within microscopic approach based on the general collective Bohr model which includes the effect of coupling with the pairing vibrations. The excitation energies observed in transitional Gd and Er isotopes are reproduced in the frame of the calculation containing no free parameters.

Acta Physica Polonica Series B

The quadrupole excitations of transuranic nuclei are described dynamically in the frame of the mi... more The quadrupole excitations of transuranic nuclei are described dynamically in the frame of the microscopic collective Bohr Hamiltonian modified by adding the coupling with the pairing vibrations. The ground-state bands in No and Fm even--even isotopes are reproduced within the model containing no adjustable parameters.

Acta Physica Polonica B, 2015

Acta Physica Polonica B, 2015

The spontaneous chiral symmetry breaking was experimentally studied at the Heavy Ion Laboratory o... more The spontaneous chiral symmetry breaking was experimentally studied at the Heavy Ion Laboratory of the University of Warsaw by use of the DSAM and DCO analysis. Obtained lifetimes, branching ratios and E2/M1 mixing ratios were used to determine B(M1) and B(E2) values. The preliminary results for 124 Cs confirm spontaneous chiral symmetry breaking hypothesis in the 15-20 spin range.