T. M. Kowalewski
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
T. M. Kowalewski has a total of 141 co-authors. Here are the top co-authors by number of shared publications:
- Akaa D. Ayangeakaa
University of North Carolina at Chapel Hill
6 shared publications - Antonella Saracino
University of North Carolina Chapel Hill
6 shared publications - Claus Müller-Gatermann
Argonne National Laboratory
6 shared publications - Nirupama Sensharma
Argonne National Laboratory
6 shared publications - Robert V. F. Janssens
University of North Carolina at Chapel Hill
6 shared publications D. Seweryniak
Physics Division Argonne National Laboratory 60439 Lemont Illinois USA
5 shared publications
Latest Publications
- 23 June 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 136 (25) , 252501
Low-Energy Dipole Strength Distribution in Ru 102 : Coexistence of Scissors and Octupole Resonances
The dipole response of ^{102}Ru has been investigated for the first time using nuclear resonance fluorescence, providing comprehensive and detailed information about the nucleus. The M1 strength, concentrated in the 3-4 MeV region, is consistent with a scissors resonance. As a surprising new feature, a pronounced E1 resonancelike structure at 4.5-5.5 MeV has been found. It is interpreted as an octupole resonance and provides evidence for low-spin octupole correlations in this excitation energy regime. The experimental results are compared with quasiparticle random phase approximation calculations, which reproduce the gross features of the cumulative strength. These observations support the coexistence of M1 scissors and octupole-induced E1 resonances as a general feature of deformed nuclei with octupole softness.
- 23 June 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 136 (25) , 252501
Low-Energy Dipole Strength Distribution in Ru 102 : Coexistence of Scissors and Octupole Resonances
The dipole response of ^{102}Ru has been investigated for the first time using nuclear resonance fluorescence, providing comprehensive and detailed information about the nucleus. The M1 strength, concentrated in the 3-4 MeV region, is consistent with a scissors resonance. As a surprising new feature, a pronounced E1 resonancelike structure at 4.5-5.5 MeV has been found. It is interpreted as an octupole resonance and provides evidence for low-spin octupole correlations in this excitation energy regime. The experimental results are compared with quasiparticle random phase approximation calculations, which reproduce the gross features of the cumulative strength. These observations support the coexistence of M1 scissors and octupole-induced E1 resonances as a general feature of deformed nuclei with octupole softness.
- Open Access
Triaxiality and shape dynamics in $^{70}$Ge
The electromagnetic properties of low-lying states in $^{70}$Ge were investigated via multi-step Coulomb excitation of a $^{70}$Ge beam impinging on a $^{208}$Pb target at the ATLAS facility of the Argonne National Laboratory. A total of 27 transitional elements and six diagonal matrix elements coupling 11 low-lying states, were extracted from the measured cross sections. These were used to calculate reduced transition probabilities, spectroscopic quadrupole moments, and rotational invariant shape parameters, providing enhanced precision and expanding on previous studies. The experimental data were compared within several theoretical frameworks, including the generalized triaxial rotor model, configuration interaction shell-model calculations, and computations within the combined frameworks of relativistic density functional theory and the five-dimensional collective Hamiltonian. The results demonstrate a good agreement with the experimental data and, in conjunction with calculations using a two-state mixing model, support significant triaxiality and strong mixing between the $0^+_1$ and $0^+_2$ states. This results in the magnitudes of their respective quadrupole deformations $[β_\text{rms}(0^+_1) = 0.228\,(3),\,β_\text{rms}(0^+_2) = 0.273\,(1)]$ being more similar than previously observed. The implications of these results for understanding the complex shape coexistence phenomena, the role of triaxiality, and shape evolution along the Ge isotopic chain are discussed.Open AccessTriaxiality and shape dynamics in $^{70}$Ge
The electromagnetic properties of low-lying states in $^{70}$Ge were investigated via multi-step Coulomb excitation of a $^{70}$Ge beam impinging on a $^{208}$Pb target at the ATLAS facility of the Argonne National Laboratory. A total of 27 transitional elements and six diagonal matrix elements coupling 11 low-lying states, were extracted from the measured cross sections. These were used to calculate reduced transition probabilities, spectroscopic quadrupole moments, and rotational invariant shape parameters, providing enhanced precision and expanding on previous studies. The experimental data were compared within several theoretical frameworks, including the generalized triaxial rotor model, configuration interaction shell-model calculations, and computations within the combined frameworks of relativistic density functional theory and the five-dimensional collective Hamiltonian. The results demonstrate a good agreement with the experimental data and, in conjunction with calculations using a two-state mixing model, support significant triaxiality and strong mixing between the $0^+_1$ and $0^+_2$ states. This results in the magnitudes of their respective quadrupole deformations $[β_\text{rms}(0^+_1) = 0.228\,(3),\,β_\text{rms}(0^+_2) = 0.273\,(1)]$ being more similar than previously observed. The implications of these results for understanding the complex shape coexistence phenomena, the role of triaxiality, and shape evolution along the Ge isotopic chain are discussed. - Open Access
High-spin spectroscopy and the onset of quasicollective structures in $^{69}$Ga
The intermediate- and high-spin level structure of the odd-$A$ $^{69}$Ga nucleus was investigated via the $^{26}$Mg($^{48}$Ca, $p4nγ$) fusion evaporation reaction at a beam energy of 195 MeV. The experiment was performed using the Gammasphere multidetector array in conjunction with the Fragment Mass Analyzer (FMA), with mass and charge identification achieved via an ionization chamber placed at the focal plane of the spectrometer. Coincidence relationships between the $^{69}$Ga reaction products and emitted $γ$ rays were analyzed to establish the level sequences, while angular distribution and angular correlation measurements were used to propose spin and parity assignments. As a result, the level scheme of the nucleus has been considerably extended. Near the ground state, the structure of $^{69}$Ga is well described by single-particle excitations, with shell-model calculations using the JUN45 and jj44b effective interactions providing a satisfactory interpretation of the observed levels. At spins in excess of 21/2 $\hbar$, three sequences of $E2$ transitions have been delineated, suggesting the onset of collectivity. An interpretation within the framework of the tilted-axis-cranking covariant density functional theory is proposed which reveals the role of $g_{9/2}$ protons and neutrons in this angular momentum regime.Open AccessHigh-spin spectroscopy and the onset of quasicollective structures in $^{69}$Ga
The intermediate- and high-spin level structure of the odd-$A$ $^{69}$Ga nucleus was investigated via the $^{26}$Mg($^{48}$Ca, $p4nγ$) fusion evaporation reaction at a beam energy of 195 MeV. The experiment was performed using the Gammasphere multidetector array in conjunction with the Fragment Mass Analyzer (FMA), with mass and charge identification achieved via an ionization chamber placed at the focal plane of the spectrometer. Coincidence relationships between the $^{69}$Ga reaction products and emitted $γ$ rays were analyzed to establish the level sequences, while angular distribution and angular correlation measurements were used to propose spin and parity assignments. As a result, the level scheme of the nucleus has been considerably extended. Near the ground state, the structure of $^{69}$Ga is well described by single-particle excitations, with shell-model calculations using the JUN45 and jj44b effective interactions providing a satisfactory interpretation of the observed levels. At spins in excess of 21/2 $\hbar$, three sequences of $E2$ transitions have been delineated, suggesting the onset of collectivity. An interpretation within the framework of the tilted-axis-cranking covariant density functional theory is proposed which reveals the role of $g_{9/2}$ protons and neutrons in this angular momentum regime. - 25 September 2025
- Published by American Physical Society (APS) in Physical Review C
- Vol. 112 (3)
Triaxiality and shape dynamics in- 25 September 2025
- Published by American Physical Society (APS) in Physical Review C
- Vol. 112 (3)
Triaxiality and shape dynamics in- 4 August 2025
- Published by American Physical Society (APS) in Physical Review C
- Vol. 112 (2)
Evidence for triaxial shape coexistence in- 4 August 2025
- Published by American Physical Society (APS) in Physical Review C
- Vol. 112 (2)
Evidence for triaxial shape coexistence in- 7 July 2025
- Published by American Physical Society (APS) in Physical Review C
- Vol. 112 (1)
Coulomb excitation of Sr 80 and the limits of the N ≈ Z ≈ 40 island of deformation
- 7 July 2025
- Published by American Physical Society (APS) in Physical Review C
- Vol. 112 (1)
Coulomb excitation of Sr 80 and the limits of the N ≈ Z ≈ 40 island of deformation
- Top Cited PapersOpen Access
- 14 February 2025
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 134 (6) , 062502
Deformation and Collectivity in Doubly MagicLead-208 is the heaviest known doubly magic nucleus and its structure is therefore of special interest. Despite this magicity, which acts to provide a strong restorative force toward sphericity, it is known to exhibit both strong octupole correlations and some of the strongest quadrupole collectivity observed in doubly magic systems. In this Letter, we employ state-of-the-art experimental equipment to conclusively demonstrate, through four Coulomb-excitation measurements, the presence of a large, negative, spectroscopic quadrupole moment for both the vibrational octupole 3 1 − and quadrupole 2 1 + state, indicative of a preference for prolate deformation of the states. The observed quadrupole moment is discussed in the context of the expected splitting of the 3 − ⊗ 3 − two-phonon states, due to the coupling of the quadrupole and octupole motion. These results are compared with theoretical values from three different methods, which are unable to reproduce both the sign and magnitude of this deformation. Thus, in spite of its well-studied nature, Pb 208 remains a puzzle for our understanding of nuclear structure.
- 14 February 2025
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 134 (6) , 062502
Top Cited PapersOpen AccessDeformation and Collectivity in Doubly MagicLead-208 is the heaviest known doubly magic nucleus and its structure is therefore of special interest. Despite this magicity, which acts to provide a strong restorative force toward sphericity, it is known to exhibit both strong octupole correlations and some of the strongest quadrupole collectivity observed in doubly magic systems. In this Letter, we employ state-of-the-art experimental equipment to conclusively demonstrate, through four Coulomb-excitation measurements, the presence of a large, negative, spectroscopic quadrupole moment for both the vibrational octupole 3 1 − and quadrupole 2 1 + state, indicative of a preference for prolate deformation of the states. The observed quadrupole moment is discussed in the context of the expected splitting of the 3 − ⊗ 3 − two-phonon states, due to the coupling of the quadrupole and octupole motion. These results are compared with theoretical values from three different methods, which are unable to reproduce both the sign and magnitude of this deformation. Thus, in spite of its well-studied nature, Pb 208 remains a puzzle for our understanding of nuclear structure.
- 16 February 2024
- Published by American Physical Society (APS) in Physical Review C
- Vol. 109 (2) , 024319
Collective modes of excitation inMedium and high-spin level sequences in were investigated using the complex multinucleon transfer reaction. The experiment was performed at the ATLAS accelerator facility at the Argonne National Laboratory using the Gammasphere array and the fragment mass analyzer (FMA). Two high-spin, quasirotational bands consisting of stretched- transitions were observed in coincidence with the known low-spin structure for the first time. These bands share remarkable similarities with highly deformed and/or superdeformed bands observed in the mass region. In addition, a regular dipole sequence with weak crossover transitions was observed. A general discussion of the observed structures, complemented by theoretical calculations carried out within the framework of the adiabatic and configuration-fixed constrained covariant density functional theory and the quantum particle-rotor model, are presented. The results are interpreted in the context of shell-structure evolution and the collectivity in the mass region.- 16 February 2024
- Published by American Physical Society (APS) in Physical Review C
- Vol. 109 (2) , 024319
Collective modes of excitation inMedium and high-spin level sequences in were investigated using the complex multinucleon transfer reaction. The experiment was performed at the ATLAS accelerator facility at the Argonne National Laboratory using the Gammasphere array and the fragment mass analyzer (FMA). Two high-spin, quasirotational bands consisting of stretched- transitions were observed in coincidence with the known low-spin structure for the first time. These bands share remarkable similarities with highly deformed and/or superdeformed bands observed in the mass region. In addition, a regular dipole sequence with weak crossover transitions was observed. A general discussion of the observed structures, complemented by theoretical calculations carried out within the framework of the adiabatic and configuration-fixed constrained covariant density functional theory and the quantum particle-rotor model, are presented. The results are interpreted in the context of shell-structure evolution and the collectivity in the mass region.