Magnetic dipole excitations in nuclei: elementary modes of nucleonic motion

Abstract

The nucleus is one of the most multi-faceted many-body systems in the universe. It exhibits a multitude of responses depending on the way one 'probes' it. With increasing technical advancements of beams at the various accelerators and of detection systems the nucleus has, over and over again, surprised us by expressing always new ways of 'organized' structures and layers of complexity. Nuclear magnetism is one of those fascinating faces of the atomic nucleus we discuss in the present review. We shall not just limit ourselves to presenting the by now very large data set that has been obtained in the last two decades using various probes, electromagnetic and hadronic alike and that presents ample evidence for a low-lying orbital scissors mode around 3 MeV, albeit fragmented over an energy interval of the order of 1.5 MeV, and higher-lying spin-flip strength in the energy region 5 - 9 MeV in deformed nuclei, nor to the presently discovered evidence for low-lying proton-neutron isovector quadrupole excitations in spherical nuclei. To the contrary, we put the experimental evidence in the perspectives of understanding the atomic nucleus and its various structures of well-organized modes of motion and thus enlarge our discussion to more general fermion and bosonic many-body systems.

59 pages, 59 figures, accepted for publication in Rev. Mod. Phys.

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• Theory of ultracold Fermi gases
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• Effects of Inelastic Neutrino-Nucleus Scattering on Supernova Dynamics and Radiated Neutrino Spectra
• Relativistic RPA in axial symmetry
• Phase structure of the two-fluid proton-neutron system
• R-process nucleosynthesis calculations with complete nuclear physics input
• Microscopic Restoration of Proton-Neutron Mixed Symmetry in Weakly Collective Nuclei
• The Nuclear Scissors Mode from Various Aspects
• Magnetic dipole probes of the sd and pf shell crossing in the A=36,38 argon isotopes
• Nuclear Scissors with Pairing and Continuity Equation
• Nuclear Scissors Mode with Pairing
• Scissors modes in crystals with cubic symmetry
• Exciting the Scissors Mode in crystals with strong spin-orbit coupling as in Bose-Einstein Condensates
• Spin-Orbit Locking and Scissors Modes in rare earth crystals with uniaxial symmetry

Cited by in corpus (105)

• Complete electric dipole response and the neutron skin in 208Pb
• Electric dipole polarizability of ${}^{48}$Ca and implications for the neutron skin
• Overview of Neutron-Proton Pairing
• Reference Database for Photon Strength Functions
• Symmetry-guided large-scale shell-model theory
• Low-energy enhancement of magnetic dipole radiation
• Dipole polarizability of 120Sn and nuclear energy density functionals
• Pygmy dipole resonance in 208Pb
• Effects of symmetry breaking in finite quantum systems
• Evidence for dipole nature of the low-energy $\gamma$ enhancement in ${}^{56}$Fe
• Large low-energy $M1$ strength for ${}^{56,57}$Fe within the nuclear shell model
• Scissors resonance in the quasi-continuum of Th, Pa and U isotopes
• Low-energy electric dipole response in 120Sn
• Novel Techniques for Constraining Neutron-Capture Rates Relevant for r-Process Heavy-Element Nucleosynthesis
• Observation of large scissors resonance strength in actinides
• Verification of detailed balance for $\gamma$ absorption and emission in Dy isotopes
• Low-energy dipole strength in 112,120Sn
• Electric and magnetic dipole modes in high-resolution inelastic proton scattering at $0^{\circ }$
• Specific features and symmetries for magnetic and chiral bands in nuclei
• First observation of low-energy γ-ray enhancement in the rare-earth region
• Estimation of M1 scissors mode strength for deformed nuclei in the medium to heavy mass region by statistical Hauser-Feshbach model calculations
• The high-efficiency γ-ray spectroscopy setup γ3 at HIγS
• Fine structure of the isovector giant dipole resonance in 208Pb: Characteristic scales and level densities
• Pygmy and core polarization dipole modes in ${}^{206}$Pb: connecting nuclear structure to stellar nucleosynthesis
• Test of the Brink-Axel hypothesis for the pygmy dipole resonance
• Electric and magnetic dipole strength in 112,114,116,118,120,124Sn
• Electromagnetic M1 transition strengths from inelastic proton scattering: The cases of 48Ca and 208Pb
• Origin of Low-Lying Enhanced E1 Strength in Rare-Earth Nuclei
• Electric dipole response of 208Pb from proton inelastic scattering: constraints on neutron skin thickness and symmetry energy
• The electric dipole response of ${}^{76}$Se above 4 MeV
• Understanding the Low-Energy Enhancement of the $\gamma$-ray Strength Function of ${}^{56}$Fe
• Neutrino-pair emission from nuclear de-excitation in core-collapse supernova simulations
• Effective Field Theory for Finite Systems with Spontaneously Broken Symmetry
• Enhanced low-energy $\gamma$-decay strength of ${}^{70}$Ni and its robustness within the shell model
• QRPA treatment of the transverse wobbling mode reconsidered
• Low energy magnetic radiation enhancement in the f${}_{7/2}$ shell
• Spin Scissors Mode and the Fine Structure of M1 States in Nuclei
• Magnetic dipole excitations of ${}^{50}$Cr
• Gamma strength function and level density of ${}^{208}$Pb from forward-angle proton scattering at 295 MeV
• Magnetic dipole excitations based on the relativistic nuclear energy density functional
• Probing Surface Quantum Flows in Deformed Pygmy Dipole Modes
• Experimental status of the nuclear spin scissors mode
• Nuclear level densities and gamma-ray strength functions in samarium isotopes
• A new type of nuclear collective motion - the spin scissors mode
• Origin of fine structure of the giant dipole resonance in sd-shell nuclei
• Spin-isospin Response in Finite Nuclei from an Extended Skyrme Interaction
• Search for weak M1 transitions in ${}^{48}$Ca with inelastic proton scattering
• Shell model description of Gamow-Teller strengths in $pf$-shell nuclei
• Transition sum rules in the shell model
• Elastic magnetic electron scattering from deformed nuclei
• Breaking of axial symmetry in excited heavy nuclei as identified in Giant Dipole Resonance data
• Studies of the Giant Dipole Resonance in ${}^{27}$Al, ${}^{40}$Ca, ${}^{56}$Fe, ${}^{58}$Ni and ${}^{208}$Pb with high energy-resolution inelastic proton scattering under 0${}^{\circ }$
• Nuclear level densities and gamma-ray strength functions of ${}^{180,181,182}$Ta
• Nuclear shape transitions and elastic magnetic electron scattering
• Statistical properties of the well deformed ${}^{153,155}$Sm nuclei and the scissors resonance
• Mixed-symmetry octupole and hexadecapole excitations in the N=52 isotones
• Properties of the first excited state of 9Be derived from (gamma,n) and (e,e') reactions
• Microscopic analysis of low-energy spin and orbital magnetic dipole excitations in deformed nuclei
• Effective Field Theory of Emergent Symmetry Breaking in Deformed Atomic Nuclei
• Role of residual interaction in the relativistic description of M1 excitation
• Experimentally constrained ${}^{165,166}\text{Ho}(n,\gamma )$ rates and implications for the $s$ process
• Evolution of low-lying M1 modes in germanium isotopes
• Restricted spin-range correction in the Oslo Method: The example of nuclear level density and $\gamma$-ray strength function from ${}^{239}\mathrm{Pu}(\mathrm{d},\mathrm{p}\gamma {)}^{240}\mathrm{Pu}$
• Non-iterative finite amplitude methods for E1 and M1 giant resonances
• Broken axial symmetry as essential feature to predict radiative capture in heavy nuclei
• Magnetic dipole excitation and its sum rule in nuclei with two valence nucleons
• Magnetic dipole transition in ${}^{48}$Ca
• Effective field theory for deformed atomic nuclei
• The scissors mode from a different perspective
• Broken axial symmetry as essential feature for a consistent modelling of various observables in heavy nuclei
• The evolution of magnetic dipole strength in ${}^{100-140}$ Sn isotope chain and quenching of nucleon g factors
• Multiple $SU(3)$ algebras in interacting boson model and shell model: Results for $(\beta ,\gamma$) bands and scissors $1^{+}$ band
• Low-energy enhancement in the magnetic dipole $\gamma$-ray strength functions of heavy nuclei
• QRPA calculations for M1 transitions with the noniterative finite amplitude method and the application to neutron radiative capture cross sections
• Rotational states in deformed nuclei: An analytic approach
• Low-energy behavior of $E2$ strength functions
• Scissors Modes:The first overtone
• Electric and magnetic dipole strength in ${}^{58}$Ni from forward-angle inelastic proton scattering
• The Spin and Orbital Contributions to Magnetic Dipole Transitions
• Matrix Model of Strength Distribution: Extension and Phase Transition
• Electric dipole polarizability constraints on neutron skin and symmetry energy
• Effect of broken axial symmetry on the electric dipole strength and the collective enhancement of level densities in heavy nuclei
• Magnetic quadrupole transitions in the relativistic energy density functional theory
• Isovector spin susceptibility: Isotopic evolution of collectivity in spin response
• Validation of Geant4's G4NRF module against nuclear resonance fluorescence data from ${}^{238}$U and ${}^{27}$Al
• Entanglement in the states of the Two-Rotor-Model
• Triplet structure of nuclear scissors mode
• Symmetry breaking of Gamow-Teller and magnetic-dipole transitions and its restoration in calcium isotopes
• Consequences of broken axial symmetry in heavy nuclei -- an overview of the situation in the valley of stability
• The scientific legacy of J. P. Elliott
• Scissors Modes: The elusive breathing overtone
• Correlations between charge radii, E0 transitions, and M1 strength
• Analytic approach to nuclear rotational states: The role of spin - A minimal model -
• Nuclear scissors modes and hidden angular momenta
• Distribution of Magnetic Dipole Strength -Binning
• Matrix Models of Strength Distributions
• Impact of restricted spin-ranges in the Oslo Method: The example of (d,p)${}^{240}\mathrm{Pu}$
• SU(3) partial dynamical symmetry and nuclear shapes
• Microscopic analysis of dipole electric and magnetic strengths in ${}^{156}$Gd
• New data acquisition system of the Lintott magnetic spectrometer at the S-DALINAC
• Positive and negative parity states of the Two-Rotor Model and scissors modes
• Azimuthal angle distributions of neutrons emitted from the ${}^9$Be($\gamma$,$n$) reaction with linearly polarized $\gamma$-rays
• A detailed view at magnetic dipole strengths: The case of semi-magic ${}^{50}$Ti
• Impact of octupole deformation on the nuclear electromagnetic response
• Comprehensive test of the Brink-Axel hypothesis in the energy region of the pygmy dipole resonance