B. Quintana - Academia.edu (original) (raw)

Papers by B. Quintana

Czechoslovak Journal of Physics, 2001

The near' proton drip-line nucleus 12epr was studied via in-beam v-ray spectroscopy using the 4~ ... more The near' proton drip-line nucleus 12epr was studied via in-beam v-ray spectroscopy using the 4~ reaction at 190 MeV. We observed for the first time excited states above the known isomer in this nucleus, up to spin 31h. The observed band is assigned to a 7rh11/2 @ vhH/2 configuration. The experimental information suggest a spin 8 + for the lowest observed state. With such a spin assignment the excitation energy of the excited states in 12epr and ~2SPr get smaller than in the heavier Pr isotopes, suggesting a sudden change in deformation close to the proton drip line.

The European Physical Journal A, 2001

Gamma ray transitions de-exciting states in the N = Z nucleus 70 Br have been identified for the ... more Gamma ray transitions de-exciting states in the N = Z nucleus 70 Br have been identified for the first time using the GASP and EUROBALL arrays coupled with ancillary detectors. The level scheme of 70 Br has been established by means of particle-gated γ-γ and γ-γ-γ coincidences. The Coulomb energy differences between isobaric analogue states in 70 Br and 70 Se show a deviation from the expected behaviour which could be related to dripline effects.

Physical Review Letters, 2015

The isospin mixing was deduced in the compound nucleus 80 Zr at an excitation energy of E Ã ¼ 54 ... more The isospin mixing was deduced in the compound nucleus 80 Zr at an excitation energy of E Ã ¼ 54 MeV from the γ decay of the giant dipole resonance. The reaction 40 Ca þ 40 Ca at E beam ¼ 136 MeV was used to form the compound nucleus in the isospin I ¼ 0 channel, while the reaction 37 Cl þ 44 Ca at E beam ¼ 95 MeV was used as the reference reaction. The γ rays were detected with the AGATA demonstrator array coupled with LaBr 3 :Ce detectors. The temperature dependence of the isospin mixing was obtained and the zero-temperature value deduced. The isospin-symmetry-breaking correction δ C used for the Fermi superallowed transitions was extracted and found to be consistent with β-decay data.

Applied Radiation and Isotopes, 2019

In order to establish the chronology of deep-sea sediments from high-resolution 210 Pb-dating, th... more In order to establish the chronology of deep-sea sediments from high-resolution 210 Pb-dating, the determination of 210 Pb and 226 Ra activity concentrations needs to be improved. Gamma spectrometry allows determining simultaneously both radionuclides. However, spectrum background is still an issue to obtain high sensitivity. Four deep-sea sediment cores were dated using Mazinger, a gamma spectrometer with high-efficiency and very low-background, and the Constant Rate and Supply model was applied to obtain recent ages.

Introducción Son muchos los estudios ambientales que requieren de la medida de radionúclidos natu... more Introducción Son muchos los estudios ambientales que requieren de la medida de radionúclidos naturales como 210Pb, 226Ra, 228Th, 230Th, 232Th, 235U y 238U. Por formar parte del fondo natural, todos ellos contribuyen a la dosis a la que la población está expuesta1, por lo tanto, una alteración de las concentraciones en las que se encuentran en la naturaleza debe ser vigilada. Los cambios en la distribución de estos radionúclidos pueden producirse tanto en la industria nuclear, sobre todo en actividades mineras y de preconcentración del uranio2, ...

The γ decay from the high-lying states of ^140Ce excited via inelastic scattering of ^17O at a bo... more The γ decay from the high-lying states of ^140Ce excited via inelastic scattering of ^17O at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented Δ E-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1^− states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1^− pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used.

Quaternary International, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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, 2015

Background: Nuclear structure information for the neutron-rich actinide nuclei is important since... more Background: Nuclear structure information for the neutron-rich actinide nuclei is important since it is the benchmark for theoretical models that provide predictions for the heaviest nuclei. Purpose: γ-ray spectroscopy of neutron-rich heavy nuclei in the actinide region. Method: Multinucleon-transfer reactions in 70 Zn + 238 U and 136 Xe + 238 U have been measured in two experiments performed at the INFN Legnaro, Italy. In the 70 Zn experiment the high-resolution HPGe Clover Array (CLARA) coupled to the magnetic spectrometer PRISMA was employed. In the 136 Xe experiment the high-resolution Advanced Gamma Tracking Array (AGATA) was used in combination with PRISMA and the Detector Array for Multinucleon Transfer Ejectiles (DANTE). Results: The ground-state band (g.s. band) of 240 U was measured up to the 20 + level and a tentative assignment was made up to the (24 +) level. Results from γ γ coincidence and from particle coincidence analyses are shown. Moments of inertia (MoI) show a clear upbend. Evidence for an extended first negative-parity band of 240 U is found. Conclusions: A detailed comparison with latest calculations shows best agreement with cranked relativistic Hartree-Bogoliubov (CRHB) calculations for the g.s. band properties. The negative-parity band shows the characteristics of a K π = 0 − band based on an octupole vibration.

Physics Letters B, 2003

The N = Z nucleus 64 Ge has been investigated in two experiments using the EUROBALL III and EUROB... more The N = Z nucleus 64 Ge has been investigated in two experiments using the EUROBALL III and EUROBALL IV spectrometers coupled to ancillary devices. Multipole mixing ratios, linear polarization and picosecond lifetimes for various transitions have been measured. The linear polarization results determine unambiguously the multipole character of the 5 − → 4 + 1665 keV transition, allowing to extract the electric dipole strength and to investigate for the first time the amount of isospin mixing implied by the presence of a forbidden E1 transition.

International Journal of Modern Physics E, 2004

Neutron rich nuclei have been populated using the 82 Se +192 Os deep-inelastic reaction. New expe... more Neutron rich nuclei have been populated using the 82 Se +192 Os deep-inelastic reaction. New experimental results on 188 W , 188,190 Os target-like nuclei, as well as 74,76,78 Ge beam-like nuclei are presented.

Inpc 2013 - International Nuclear Physics Conference, Vol. 1, 2014

The study of the collective properties of nuclear excitations far from stability provides informa... more The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic observables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope (64 Ni) towards the 78 Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently performed an experiment with the goal to extract the B(E2; 0 + → 2 +) value for the 74 Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed. 66 epjconf EPJ Web of Conferences This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Physical Review Letters, 2014

Physical Review C, 2002

The yrast band of the NϭZ nucleus 84 Mo has been extended up to the 10 ϩ state. Its moment of ine... more The yrast band of the NϭZ nucleus 84 Mo has been extended up to the 10 ϩ state. Its moment of inertia varies smoothly up to this state ͑rotational frequency 0.6 MeV͒. The new data confirm the systematic delay of the particle alignment frequency in NϭZ nuclei with respect to the neighboring NϾZ nuclei, which has been suggested as a signature of the neutron-proton pairing interaction. Projected shell model calculations performed for the heaviest NϭZ nuclei studied so far, 84 Mo and 88 Ru, predict that the confirmation of a possible enhancement of the neutron-proton residual interaction requires the observation of still higher spins in these nuclei.

Physical Review C, 2005

The nucleus 34 S has been studied up to relatively high spin (I = 10h) and up to an excitation en... more The nucleus 34 S has been studied up to relatively high spin (I = 10h) and up to an excitation energy of 16.64 MeV. Data are compared with different shell model calculations where effective interactions involving two main shells, the sd and the fp, are used. For the first time in an N = Z nucleus, it is observed that the promotion of an isoscalar (T = 0) proton-neutron pair to the fp shell becomes energetically favored at high spin.

Physical Review C, 2004

... T. Martinez, 1 R. Menegazzo, 3 DR Napoli, 1 B. Quintana, 5 P. Spolaore, 1 YH Zhang, 1 and J. ... more ... T. Martinez, 1 R. Menegazzo, 3 DR Napoli, 1 B. Quintana, 5 P. Spolaore, 1 YH Zhang, 1 and J. Wrzesinski 4 ... From the region NZ 40 to nuclei close to NZ 50 there is a dramatic structure evolution from strongly deformed nuclei to spherical (“shell model”) ones, challenging the ...

Physical Review C, 2002

... PMK I is the angular mo-mentum projector 25 which projects good angular momen-tum from an int... more ... PMK I is the angular mo-mentum projector 25 which projects good angular momen-tum from an intrinsic state . In this way, angular mo-mentum conservation, which is violated in the deformed mean-field calculation, is restored. ...

Journal of Physics G: Nuclear and Particle Physics, 2005

Several nuclei in the A ∼ 190 region have been studied following deep-inelastic reactions using a... more Several nuclei in the A ∼ 190 region have been studied following deep-inelastic reactions using a 460 MeV 82 Se projectile impinging upon a thick 192 Os target. The GASP array (at the Legnaro National Laboratory in Italy) was used to measure the resulting γ-decays. The previously reported near-yrast structure of 191 Os is extended to a t 1 2 = 61 ns isomer, at an energy of 2640 keV. Branching ratios for I = 1 and I = 2 transitions in the K π = 11

The European Physical Journal A, 2003

Following the commissioning of the PRISMA large-acceptance spectrometer, installed at the Laborat... more Following the commissioning of the PRISMA large-acceptance spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), an international nuclear-structure collaboration has started to develop a large γ-ray setup to be installed in the target position of the spectrometer. The array is based on the EUROBALL composite CLOVER detectors. In this contribution the CLOVER detector array is described and its expected performance figures discussed. This new setup, by using the high-intensity heavyion beams provided by the LNL ALPI linac, will push the study of nuclear structure towards moderately neutron-rich nuclei by means of quasi-elastic and deep inelastic reactions.

Czechoslovak Journal of Physics, 2001

The near' proton drip-line nucleus 12epr was studied via in-beam v-ray spectroscopy using the 4~ ... more The near' proton drip-line nucleus 12epr was studied via in-beam v-ray spectroscopy using the 4~ reaction at 190 MeV. We observed for the first time excited states above the known isomer in this nucleus, up to spin 31h. The observed band is assigned to a 7rh11/2 @ vhH/2 configuration. The experimental information suggest a spin 8 + for the lowest observed state. With such a spin assignment the excitation energy of the excited states in 12epr and ~2SPr get smaller than in the heavier Pr isotopes, suggesting a sudden change in deformation close to the proton drip line.

The European Physical Journal A, 2001

Gamma ray transitions de-exciting states in the N = Z nucleus 70 Br have been identified for the ... more Gamma ray transitions de-exciting states in the N = Z nucleus 70 Br have been identified for the first time using the GASP and EUROBALL arrays coupled with ancillary detectors. The level scheme of 70 Br has been established by means of particle-gated γ-γ and γ-γ-γ coincidences. The Coulomb energy differences between isobaric analogue states in 70 Br and 70 Se show a deviation from the expected behaviour which could be related to dripline effects.

Physical Review Letters, 2015

The isospin mixing was deduced in the compound nucleus 80 Zr at an excitation energy of E Ã ¼ 54 ... more The isospin mixing was deduced in the compound nucleus 80 Zr at an excitation energy of E Ã ¼ 54 MeV from the γ decay of the giant dipole resonance. The reaction 40 Ca þ 40 Ca at E beam ¼ 136 MeV was used to form the compound nucleus in the isospin I ¼ 0 channel, while the reaction 37 Cl þ 44 Ca at E beam ¼ 95 MeV was used as the reference reaction. The γ rays were detected with the AGATA demonstrator array coupled with LaBr 3 :Ce detectors. The temperature dependence of the isospin mixing was obtained and the zero-temperature value deduced. The isospin-symmetry-breaking correction δ C used for the Fermi superallowed transitions was extracted and found to be consistent with β-decay data.

Applied Radiation and Isotopes, 2019

In order to establish the chronology of deep-sea sediments from high-resolution 210 Pb-dating, th... more In order to establish the chronology of deep-sea sediments from high-resolution 210 Pb-dating, the determination of 210 Pb and 226 Ra activity concentrations needs to be improved. Gamma spectrometry allows determining simultaneously both radionuclides. However, spectrum background is still an issue to obtain high sensitivity. Four deep-sea sediment cores were dated using Mazinger, a gamma spectrometer with high-efficiency and very low-background, and the Constant Rate and Supply model was applied to obtain recent ages.

Introducción Son muchos los estudios ambientales que requieren de la medida de radionúclidos natu... more Introducción Son muchos los estudios ambientales que requieren de la medida de radionúclidos naturales como 210Pb, 226Ra, 228Th, 230Th, 232Th, 235U y 238U. Por formar parte del fondo natural, todos ellos contribuyen a la dosis a la que la población está expuesta1, por lo tanto, una alteración de las concentraciones en las que se encuentran en la naturaleza debe ser vigilada. Los cambios en la distribución de estos radionúclidos pueden producirse tanto en la industria nuclear, sobre todo en actividades mineras y de preconcentración del uranio2, ...

The γ decay from the high-lying states of ^140Ce excited via inelastic scattering of ^17O at a bo... more The γ decay from the high-lying states of ^140Ce excited via inelastic scattering of ^17O at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented Δ E-E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1^− states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1^− pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used.

Quaternary International, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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, 2015

Background: Nuclear structure information for the neutron-rich actinide nuclei is important since... more Background: Nuclear structure information for the neutron-rich actinide nuclei is important since it is the benchmark for theoretical models that provide predictions for the heaviest nuclei. Purpose: γ-ray spectroscopy of neutron-rich heavy nuclei in the actinide region. Method: Multinucleon-transfer reactions in 70 Zn + 238 U and 136 Xe + 238 U have been measured in two experiments performed at the INFN Legnaro, Italy. In the 70 Zn experiment the high-resolution HPGe Clover Array (CLARA) coupled to the magnetic spectrometer PRISMA was employed. In the 136 Xe experiment the high-resolution Advanced Gamma Tracking Array (AGATA) was used in combination with PRISMA and the Detector Array for Multinucleon Transfer Ejectiles (DANTE). Results: The ground-state band (g.s. band) of 240 U was measured up to the 20 + level and a tentative assignment was made up to the (24 +) level. Results from γ γ coincidence and from particle coincidence analyses are shown. Moments of inertia (MoI) show a clear upbend. Evidence for an extended first negative-parity band of 240 U is found. Conclusions: A detailed comparison with latest calculations shows best agreement with cranked relativistic Hartree-Bogoliubov (CRHB) calculations for the g.s. band properties. The negative-parity band shows the characteristics of a K π = 0 − band based on an octupole vibration.

Physics Letters B, 2003

The N = Z nucleus 64 Ge has been investigated in two experiments using the EUROBALL III and EUROB... more The N = Z nucleus 64 Ge has been investigated in two experiments using the EUROBALL III and EUROBALL IV spectrometers coupled to ancillary devices. Multipole mixing ratios, linear polarization and picosecond lifetimes for various transitions have been measured. The linear polarization results determine unambiguously the multipole character of the 5 − → 4 + 1665 keV transition, allowing to extract the electric dipole strength and to investigate for the first time the amount of isospin mixing implied by the presence of a forbidden E1 transition.

International Journal of Modern Physics E, 2004

Neutron rich nuclei have been populated using the 82 Se +192 Os deep-inelastic reaction. New expe... more Neutron rich nuclei have been populated using the 82 Se +192 Os deep-inelastic reaction. New experimental results on 188 W , 188,190 Os target-like nuclei, as well as 74,76,78 Ge beam-like nuclei are presented.

Inpc 2013 - International Nuclear Physics Conference, Vol. 1, 2014

The study of the collective properties of nuclear excitations far from stability provides informa... more The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic observables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope (64 Ni) towards the 78 Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently performed an experiment with the goal to extract the B(E2; 0 + → 2 +) value for the 74 Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed. 66 epjconf EPJ Web of Conferences This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Physical Review Letters, 2014

Physical Review C, 2002

The yrast band of the NϭZ nucleus 84 Mo has been extended up to the 10 ϩ state. Its moment of ine... more The yrast band of the NϭZ nucleus 84 Mo has been extended up to the 10 ϩ state. Its moment of inertia varies smoothly up to this state ͑rotational frequency 0.6 MeV͒. The new data confirm the systematic delay of the particle alignment frequency in NϭZ nuclei with respect to the neighboring NϾZ nuclei, which has been suggested as a signature of the neutron-proton pairing interaction. Projected shell model calculations performed for the heaviest NϭZ nuclei studied so far, 84 Mo and 88 Ru, predict that the confirmation of a possible enhancement of the neutron-proton residual interaction requires the observation of still higher spins in these nuclei.

Physical Review C, 2005

The nucleus 34 S has been studied up to relatively high spin (I = 10h) and up to an excitation en... more The nucleus 34 S has been studied up to relatively high spin (I = 10h) and up to an excitation energy of 16.64 MeV. Data are compared with different shell model calculations where effective interactions involving two main shells, the sd and the fp, are used. For the first time in an N = Z nucleus, it is observed that the promotion of an isoscalar (T = 0) proton-neutron pair to the fp shell becomes energetically favored at high spin.

Physical Review C, 2004

... T. Martinez, 1 R. Menegazzo, 3 DR Napoli, 1 B. Quintana, 5 P. Spolaore, 1 YH Zhang, 1 and J. ... more ... T. Martinez, 1 R. Menegazzo, 3 DR Napoli, 1 B. Quintana, 5 P. Spolaore, 1 YH Zhang, 1 and J. Wrzesinski 4 ... From the region NZ 40 to nuclei close to NZ 50 there is a dramatic structure evolution from strongly deformed nuclei to spherical (“shell model”) ones, challenging the ...

Physical Review C, 2002

... PMK I is the angular mo-mentum projector 25 which projects good angular momen-tum from an int... more ... PMK I is the angular mo-mentum projector 25 which projects good angular momen-tum from an intrinsic state . In this way, angular mo-mentum conservation, which is violated in the deformed mean-field calculation, is restored. ...

Journal of Physics G: Nuclear and Particle Physics, 2005

Several nuclei in the A ∼ 190 region have been studied following deep-inelastic reactions using a... more Several nuclei in the A ∼ 190 region have been studied following deep-inelastic reactions using a 460 MeV 82 Se projectile impinging upon a thick 192 Os target. The GASP array (at the Legnaro National Laboratory in Italy) was used to measure the resulting γ-decays. The previously reported near-yrast structure of 191 Os is extended to a t 1 2 = 61 ns isomer, at an energy of 2640 keV. Branching ratios for I = 1 and I = 2 transitions in the K π = 11

The European Physical Journal A, 2003

Following the commissioning of the PRISMA large-acceptance spectrometer, installed at the Laborat... more Following the commissioning of the PRISMA large-acceptance spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), an international nuclear-structure collaboration has started to develop a large γ-ray setup to be installed in the target position of the spectrometer. The array is based on the EUROBALL composite CLOVER detectors. In this contribution the CLOVER detector array is described and its expected performance figures discussed. This new setup, by using the high-intensity heavyion beams provided by the LNL ALPI linac, will push the study of nuclear structure towards moderately neutron-rich nuclei by means of quasi-elastic and deep inelastic reactions.