SwePub - search: WFRF:(Hamamoto Kuroda Ikuko)

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1.	Fujita, Y, et al. (author) Evidence for the existence of the [202]3/2 deformed band in mirror nuclei Mg-25 and Al-25 2004 In: Physical Review Letters. - 1079-7114. ; 92:6 Journal article (peer-reviewed)abstract After 50 years of its prediction, the highest-lying [2 0 2]3/2 orbit among the six Nilsson single-particle orbits originating from the sd shells in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in Al-25 at excitation energies of 6-7.5 MeV in a high-resolution Mg-25(He-3,t) charge-exchange reaction at 0degrees having a strong selectivity for Gamow-Teller transitions. In the comparison with the analogous M1 transitions in Mg-25, the J(pi)=3/2(+) bandhead state and the excited 5/2(+) and 7/2(+) members were clearly assigned.
2.	Fujita, Y., et al. (author) Identification of the [202]3/2 deformed band in mirror nuclei Mg-25 and Al-25 and implications for unstable nuclei 2006 In: Physica Scripta. - 0031-8949. ; T125, s. 194-195 Journal article (peer-reviewed)abstract Fifty years after its prediction, the highest-lying [ 2 0 2] 3) 2 orbit among the six Nilsson single-particle orbits originating from the sd shell in prolately deformed nuclei and the rotational band on this orbit were identified. The band members were observed in Al-25 at excitation energies of 6-7.5MeV in a high-resolution Mg-25(He-3,t) charge-exchange reaction at 0 degrees having a strong selectivity for Gamow-Teller transitions. In comparison with the analogous M1 transitions in Mg-25, the J(pi) = 3/+ band-head state and the excited 5/+ and 7/2+ members were clearly assigned.
3.	Fujita, Y., et al. (author) M1 and Gamow-Teller transitions in T=1/2 nuclei Na-23 and Mg-23 2002 In: Physical Review C: covering nuclear physics. ; 66 Journal article (peer-reviewed)
4.	Hamamoto-Kuroda, Ikuko, et al. (author) A personal view of some issues involved in the structure of nuclei with large neutron excess 2003 In: Comptes Rendus. Physique. - 1631-0705. ; 4:4-5, s. 433-436 Journal article (peer-reviewed)abstract Large neutron excess poses new issues concerning the competition of deformation and pairing as well as changes in nuclear shell structure.
5.	Hamamoto-Kuroda, Ikuko (author) Change of shell structure and magnetic moments of odd-N deformed nuclei towards the neutron drip line 2010 In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 37:5 Journal article (peer-reviewed)abstract Examples of the change of neutron shell structure in both weakly bound and resonant neutron one-particle levels in nuclei towards the neutron drip line are exhibited. It is shown that the shell-structure change due to the weak binding may lead to the deformation of those nuclei with the neutron numbers N approximate to 8, 20, 28 and 40, which are known to be magic numbers in stable nuclei. Nuclei in the 'island of inversion' are most easily and in a simple manner understood in terms of deformation. As an example of spectroscopic properties other than single-particle energies, magnetic moments of some weakly bound possibly deformed odd-N nuclei with neutron numbers close to those traditional magic numbers are given, which are calculated using the wavefunction of the last odd particle in deformed Woods-Saxon potentials.
6.	Hamamoto-Kuroda, Ikuko (author) Dominance of low-l component in weakly bound deformed single-neutron orbits 2004 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 69:4 Journal article (peer-reviewed)abstract Calculating single-particle (Nilsson) levels in axially symmetric quadrupole-deformed potentials in coordinate space, the structure of weakly bound neutron orbits is studied in the absence of pair correlation. It is shown that in the wave functions of Omega(pi)=1/2(+) orbits, where Omega expresses the projection of the particle angular momentum along the symmetry axis, the l=0 (s(1/2)) component becomes overwhelmingly dominant as the binding energy of the orbits approaches zero, irrespective of the size of the deformation and the kind of Nilsson orbits. Consequently, all Omega(pi)=1/2(+) levels become practically unavailable for both deformation and many-body pair correlation, when the levels approach continuum or lie in the continuum.
7.	Hamamoto-Kuroda, Ikuko (author) Effect of weakly-bound neutrons on pair-correlation and deformation 2005 In: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 764, s. 157-163 Conference paper (peer-reviewed)abstract The unique role of weakly-bound low-angular-momentum neutrons in the structure of neutron-drip-line nuclei is presented, studying both the many-body pair-correlation in spherical nuclei and the one-particle orbits in the deformed Woods-Saxon potential. Both the HFB equations in the former case and the Schrodinger equation in the latter are solved in coordinate space with correct asymptotic boundary conditions. Combining the results of those two cases, it is concluded, for example, that all Ωx=1/2+ one-particle levels become practically unavailable for both deformation and many-body pair-correlation, when the HF one-particle levels approach continuum or lie in the continuum
8.	Hamamoto-Kuroda, Ikuko (author) Effective pair-gap of weakly-bound neutrons in deformed nuclei 2005 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:3 Journal article (peer-reviewed)abstract The dependence of effective pair gap on weakly bound neutron orbits is studied in deformed nuclei in comparison with that in spherical nuclei, solving the Hartree-Fock-Bogoliubov equation in a simplified model in coordinate space with the correct asymptotic boundary conditions. In spherical nuclei the effective pair gap of s1/2 neutrons decreases to zero in the limit that the corresponding Hartree-Fock one-particle energy approaches zero. In the same limit, the effective pair gap of =1/2+ neutrons in deformed nuclei becomes very small when the wave functions of =1/2+ orbits contain an appreciable amount of s1/2 components, even if a considerable amount of larger-components remains in the wave functions. Then, the one-particle excitation spectra of deformed even-even neutron-drip-line nuclei, in which an =1/2+ level is weakly bound, can start at much lower energy than twice the average pair gap in the presence of many-body pair correlation.
9.	Hamamoto-Kuroda, Ikuko (author) Examining possible neutron-halo nuclei heavier than Mg 37 2017 In: Physical Review C: covering nuclear physics. - 2469-9985. ; 95:4 Journal article (peer-reviewed)abstract The even-Z odd-N neutron-halo nuclei, which are the lightest neutron-halo nuclei heavier than Mg37, are explored by studying the shell structure unique in weakly bound neutrons for spherical or deformed shapes. It is pointed out that due to the narrowed N=50 spherical energy gap and a few resulting close-lying neutron one-particle levels, 1g9/2, 3s1/2, and 2d5/2, for spherical shape, nuclei with some weakly bound neutrons filling in those levels may be deformed and have a good chance to show deformed s-wave halos. Promising candidates are Cr472471, Cr492473, Cr512475, and Fe512677 in the case that those nuclei lie inside the neutron drip line. An interesting possibility of the deformed p-wave or s-wave halos is suggested also for the nucleus Ar351853.
10.	Hamamoto-Kuroda, Ikuko, et al. (author) Further examination of prolate-shape dominance in nuclear deformation 2009 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 79:3 Journal article (peer-reviewed)abstract The observed almost complete dominance of prolate over oblate deformations in the ground states of deformed even-even nuclei is related to the splitting of high center dot "surface" orbits in the Nilsson diagram: on the oblate side the occurrence of numerous strongly avoided crossings which reduce the fanning out of the low Lambda orbits, while on the prolate side the same interactions increase the fanning out. It is further demonstrated that the prolate dominance is rather special for the restricted particle number of available nuclei and is not generic for finite systems with mean-field potentials resembling those in atomic nuclei.
11.	Hamamoto-Kuroda, Ikuko, et al. (author) Hamamoto-Kuroda, Ikuko 1988 In: Lärda Lund A-Ö. ; , s. 78-78 Book chapter (pop. science, debate, etc.)
12.	Hamamoto-Kuroda, Ikuko (author) Interplay between one-particle and collective degrees of freedom in nuclei 2016 In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 91:2 Journal article (peer-reviewed)abstract Some developments of nuclear-structure physics uniquely related to Copenhagen School are sketched based on theoretical considerations versus experimental findings and one-particle versus collective aspects. Based on my personal overview I pick up the following topics; (1) Study of vibration in terms of particle-vibration coupling; (2) one-particle motion in deformed and rotating potentials, and yrast spectroscopy in high-spin physics; (3) triaxial shape in nuclei: wobbling motion and chiral bands; (4) nuclear structure of drip line nuclei: in particular, shellstructure (or magic numbers) change and spherical or deformed halo phenomena; (5) shell structure in oblate deformation.
13.	Hamamoto-Kuroda, Ikuko (author) Interpretation of Coulomb breakup of Ne-31 in terms of deformation 2010 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 81:2 Journal article (peer-reviewed)abstract The recent experimental data on Coulomb breakup of the nucleus Ne-31 are interpreted in terms of deformation. The measured large one-neutron removal cross section indicates that the ground state of Ne-31 is either an s halo or a p halo. The data can be most easily interpreted as the spin of the ground state being 3/2(-) coming from either the Nilsson level [330 1/2] or the Nilsson level [321 3/2] depending on the neutron separation energy S-n. However, the possibility of 1/2(+) coming from [200 1/2] is not excluded. It is suggested that if the large ambiguity in the measured value of S-n of Ne-31, 0.29 +/- 1.64 MeV, can be reduced by an order of magnitude, say to be +/- 100 keV, one may get a clear picture of the spin-parity of the halo ground state.
14.	Hamamoto-Kuroda, Ikuko, et al. (author) Isoscalar dipole strength in Pb-208(82)126: The spurious mode and the strength in the continuum 2002 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 66:4 Journal article (peer-reviewed)abstract The isoscalar dipole (compression) mode is studied first using the schematic harmonic-oscillator model, and then the self-consistent Hartree-Fock (HF) and random-phase approximation (RPA) are solved in coordinate space. Taking Pb-208 and the SkyM* interaction as a numerical example, the spurious component and the strength in the continuum are carefully examined using the sum rules. It is pointed out that in the continuum calculation one has to use an extremely fine radial mesh in HF and RPA in order to separate, with good accuracy, the spurious component from intrinsic excitations.
15.	Hamamoto-Kuroda, Ikuko (author) Neutron decay width of one-particle resonant levels in deformed nuclei 2008 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:5, s. 6-054311 Journal article (peer-reviewed)abstract The neutron partial decay width of one-particle resonant levels that are the bandhead states in odd-N deformed nuclei is estimated in the formalism with a real-energy variable, using the width of one-particle resonance calculated in terms of eigenphase. It is shown that because of the presence of various (lj) components in a given one-particle resonant level of deformed nuclei, the neutron decay width can be quite different from the one obtained from assuming a spherically symmetric nuclear shape. As a numerical example, the formalism is applied to the case of the nucleus Be-13(4)9, which lies outside the neutron drip line by 100-200 kcV. Considering that the core of the nucleus consisting of four protons and eight neutrons is most likely prolately deformed, we point out the possibility that two lowest lying levels have I-pi = 1/2(+) for the N = 9 nucleus, and the higher lying one may have a neutron decay width that is much narrower than the one expected for an s(1/2) level at the same resonance energy. The structure of some Omega(pi) = 1/2(+) one-particle resonant levels, which are smoothly connected to weakly bound one-particle levels as the potential strength becomes stronger, is also analyzed using the present formalism.
16.	Hamamoto-Kuroda, Ikuko (author) Neutron shell structure and deformation in neutron-drip-line nuclei 2012 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:6 Journal article (peer-reviewed)abstract Neutron shell structure and the resulting possible deformation in the neighborhood of neutron-drip-line nuclei are systematically discussed, based on both bound and resonant neutron one-particle energies obtained from spherical and deformed Woods-Saxon potentials. Owing to the unique behavior of weakly bound and resonant neutron one-particle levels with smaller orbital angular momenta l, a systematic change in the shell structure and thereby a change in the neutron magic numbers are pointed out, compared with those of stable nuclei expected from the conventional j-j shell model. For a spherical shape with the operator of the spin-orbit potential conventionally used, the l(j) levels belonging to a given oscillator major shell with parallel spin and orbital angular momenta tend to gather together in the energetically lower half of the major shell, while the levels with antiparallel spin and orbital angular momenta gather in the upper half. This tendency leads to a unique shell structure and possible deformation when neutrons start to occupy the orbits in the lower half of the major shell. Among others, the neutron magic number N = 28 disappears and N = 50 may disappear, while the magic number N = 82 may presumably survive owing to the large l = 5 spin-orbit splitting for the 1h(11/2) orbit. On the other hand, an appreciable amount of energy gap may appear at N = 16 and 40 for spherical shape, while neutron-drip-line nuclei in the region of neutron numbers above N = 20, 40, and 82, namely, N approximate to 21-28, N approximate to 41-54, and N approximate to 83-90, may be quadrupole deformed, although the possible deformation also depends on the proton number of the respective nuclei.
17.	Hamamoto-Kuroda, Ikuko, et al. (author) New aspects of nuclear structure near drip lines 2002 In: Nuclear Physics News. ; 12:No.2, s. 21-29 Journal article (peer-reviewed)
18.	Hamamoto-Kuroda, Ikuko (author) Nilsson diagrams for light neutron-rich nuclei with weakly-bound neutrons 2007 In: Physical Review C: covering nuclear physics. ; 76 Journal article (peer-reviewed)abstract Using Woods-Saxon potentials and the eigenphase formalism for one-particle resonances, one-particle bound and resonant levels for neutrons as a function of quadrupole deformation are presented, which are supposed to be useful for the interpretation of spectroscopic properties of some light neutron-rich nuclei with weakly bound neutrons. Compared with Nilsson diagrams in textbooks that are constructed using modified oscillator potentials, we point out a systematic change of the shell structure in connection with both weakly bound and resonant one-particle levels related to small orbital angular momenta . Then, it is seen that weakly bound neutrons in nuclei such as 15-19C and 33-37Mg may prefer being deformed as a result of the Jahn-Teller effect, due to the near degeneracy of the 1d5/2-2s1/2 levels and the 1f7/2-2p3/2 levels in the spherical potential, respectively. Furthermore, the absence of some one-particle resonant levels compared with the Nilsson diagrams in textbooks is illustrated.
19.	Hamamoto-Kuroda, Ikuko (author) Nuclear wobbling-phonon excitations with alignments 2003 In: Nuclear Physics, Section A. - 0375-9474. ; 722, s. 389-394 Journal article (peer-reviewed)
20.	Hamamoto-Kuroda, Ikuko (author) Oblate deformation of light neutron-rich even-even nuclei 2014 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:5 Journal article (peer-reviewed)abstract Light neutron-rich even-even nuclei, of which the ground state is oblately deformed, are looked for, examining the Nilsson diagram based on realisticWoods-Saxon potentials. One-particle energies of the Nilsson diagram are calculated by solving the coupled differential equations obtained from the Schrodinger equation in coordinate space with the proper asymptotic behavior for r -> infinity for both one-particle bound and resonant levels. The eigenphase formalism is used in the calculation of one-particle resonant energies. Large energy gaps on the oblate side of the Nilsson diagrams are found to be related to the magic numbers for the oblate deformation of the harmonic-oscillator potential where the frequency ratios (omega(perpendicular to) : omega(z)) are simple rational numbers. In contrast, for the prolate deformation the magic numbers obtained from simple rational ratios of (omega(perpendicular to) : omega(z)) of the harmonic-oscillator potential are hardly related to the particle numbers, at which large energy gaps appear in the Nilsson diagrams based on realisticWoods-Saxon potentials. The argument for an oblate shape of Si-42(14)28 is given. Among light nuclei the nucleus C-20(6)14 is found to be a good candidate for having the oblate ground state. In the region of the mass number A approximate to 70 the oblate ground state may be found in the nuclei around Ni-76(28)48 in addition to Ni-64(28)36.
21.	Hamamoto-Kuroda, Ikuko (author) One-particle properties of deformed N approximate to 28 odd-N nuclei with weakly bound or resonant neutrons 2009 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 79:1 Journal article (peer-reviewed)abstract Possible deformation of odd-N nuclei with N approximate to 28 toward the neutron drip line is investigated using the Nilsson diagram based on deformed Woods-Saxon potentials. Both weakly-bound and resonant one-particle levels are properly obtained by directly solving the Schrodinger equation in mesh of space coordinate with the correct boundary condition. If we use the same diffuseness of the potential as that of beta-stable nuclei, the energy difference between the neutron 2p(3/2) and 1f(7/2) levels becomes very small or the N = 28 energy gap almost disappears, as the binding energies of those levels approach zero. This suggests that the ground states of those neutron drip line nuclei are likely to be deformed. In particular, the spin-parity and the magnetic moment of the ground state of odd-N nuclei, S-43(16)27 and S-45(16)29, are examined. Moreover, it is suggested that in Mg-39(12)27 lying outside the drip line the lowest resonant state may have 5/2(-), if the N = 28 energy gap almost vanishes.
22.	Hamamoto-Kuroda, Ikuko (author) One-particle resonant levels in a deformed potential 2005 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 72:2 Journal article (peer-reviewed)abstract (S)olving the Schrodinger equation in coordinate space with the appropriate asymptotic boundary conditions, neutron one-particle resonant levels in Y-20-deformed Woods-Saxon potentials are studied. These resonance levels are the natural extension of one-particle bound levels to the continuum and are defined in terms of eigenphase. For one-particle bound levels with Omega(pi)not equal 1/2(+) the corresponding one-particle resonant levels can be always found for small positive energies. For one-particle bound levels with Omega(pi)=1/2(+) the corresponding one-particle resonant levels are either absent or disappearing quickly as energy increases, when we use well-deformed potentials with a realistic size of diffuseness. The possible presence of Omega(pi)=1/2(+) one-particle resonant levels, in which epsilon=0 components in the wave functions play a crucial role, is further studied using a simplified model without spin-orbit potential.
23.	Hamamoto-Kuroda, Ikuko (author) Pair correlation in deformed neutron-drip-line nuclei: The eigenphase formalism and asymptotic behavior 2006 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 73:4 Journal article (peer-reviewed)abstract The Hartree-Fock-Bogoliubov (HFB) equation for deformed nuclei in a simplified model is solved in coordinate space with correct asymptotic boundary conditions, in order to study the pair correlation in nuclei close to the neutron drip line. The eigenphase formalism is applied, when the upper components of HFB radial wave functions are continuum wave functions. Calculated occupation probabilities of various Nilsson orbits in the HFB ground state vary smoothly from the region of the upper components being bound wave functions to that of those being continuum wave functions. It is shown that weakly-bound or resonance-like Omega(pi)=1/2(+) Nilsson orbits contribute little to the occupation probability of the HFB ground state, while the contribution by the orbits with a large value of Omega, of which the smallest possible orbital-angular-momentum is neither 0 nor 1, may be approximately estimated using the BCS formula.
24.	Hamamoto-Kuroda, Ikuko, et al. (author) Pair correlation in neutron drip line nuclei 2003 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 68:3: 034312 Journal article (peer-reviewed)abstract The Hartree-Fock-Bogoliubov (HFB) equation in a simplified model is solved in coordinate space with the correct asymptotic boundary conditions, in order to study the pair correlation in nuclei close to the neutron drip line. The occupation probability obtained in the HFB approach for lower-l orbits decreases considerably already when the binding energy of the corresponding Hartree-Fock (HF) one-particle level becomes smaller. When the HF one-particle level enters into the continuum, the lower-l orbit soon becomes almost unavailable for the pair correlation of the many-body system. In contrast, the contribution to the pair correlation by high-l orbits which have one-particle resonant levels with narrow width in the HF potential can be estimated in the BCS approximation using the one-particle resonant energies, though the associated wave functions in the HFB approach are bound-state wave functions.
25.	Hamamoto-Kuroda, Ikuko (author) Polarization charge of particles near threshold due to the coupling to shape oscillations 2002 In: Proceedings of the International Symposium on Nuclear Electro-Weak Spectroscopy for Symmetries in Electro-Weak Nuclear-Processes. in Honor of Professor Hiro Ejiri. - 9812381252 ; , s. 261-266 Conference paper (peer-reviewed)abstract It is shown that the isoscalar strength in the energy region just above the low energy threshold, which is created by exciting particles to the continuum in nuclei far from β-stability lines, can be reduced by the attractive coupling to isoscalar shape oscillations. This is in contrast to the well known fact that in β-stable nuclei low lying isoscalar particle hole strengths are always increased by the attractive isoscalar coupling, which leads to an appreciable amount of positive polarization charge. On the other hand, the core polarization effect on bound particles with l=0 and 1 is always positive, but vanishes as the binding energy approaches to zero
26.	Hamamoto-Kuroda, Ikuko (author) Positive-energy one-particle levels in quadrupole-deformed Woods-Saxon potentials 2006 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 73:6 Journal article (peer-reviewed)abstract Positive-energy one-particle levels for neutrons in Y20 deformed Woods-Saxon potentials are examined using the eigenphase representation. Taking the example of =1/2+ levels, not only one-particle resonant levels but also all solutions in the eigenphase representation within a model space are studied. It is shown that a particular eigenphase solution among an infinite number of eigenphase solutions at a given energy plays a crucial role in producing low-lying one-particle resonance, whereas for the excitation energy lower than a few MeV the eigenphase sum is almost equal to the particular eigenphase when the sum is expressed by the value mod n. Some one-particle resonant levels defined in terms of eigenphase, which have no correspondence to any bound one-particle levels, are found and discussed. It is shown that the relative probability of the s1/2 component estimated using the probabilities inside the Woods-Saxon potentials is a decisive factor for obtaining one-particle resonant levels as a continuation of weakly bound =1/2+ levels.
27.	Hamamoto-Kuroda, Ikuko (author) Possible presence and properties of multi-chiral-pair bands in odd-odd nuclei with the same intrinsic configuration 2013 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:2 Journal article (peer-reviewed)abstract Applying a relatively simple particle-rotor model to odd-odd nuclei, the possible presence of multi-chiral-pair bands is looked for, where chiral-pair bands are defined not only by near degeneracy of the levels of two bands but also by similar expectation values of squared components of three angular momenta that define chirality. In the angular-momentum region where two pairs of chiral-pair bands are obtained, the possible interband M1/E2 decay from the second-lowest chiral-pair bands to the lowest chiral-pair bands is studied, with the intention of finding how to experimentally identify the multi-chiral-pair bands. It is found that up until almost the bandhead the intraband M1/E2 decay within the second chiral-pair bands is preferred rather than the interband M1/E2 decay to the lowest chiral-pair bands, though the decay possibility depends on the ratio of actual decay energies. It is also found that chiral-pair bands in our model and definition are hardly obtained for gamma values outside the range 25 degrees < gamma < 35 degrees, although either a near-degeneracy or a constant energy difference of several hundred keV between the two levels for a given angular momentum I in "a pair bands" is sometimes obtained in some limited region of I. In the present model calculations the energy difference between chiral-pair bands is always one or two orders of magnitude smaller than a few hundred keV, and no chiral-pair bands are obtained, which have an almost constant energy difference of the order of a few hundred keV in a reasonable range of I.
28.	Hamamoto-Kuroda, Ikuko, et al. (author) Properties of Be-12 and Be-11 in terms of single-particle motion in deformed potential 2007 In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 34, s. 2715-2725 Journal article (peer-reviewed)
29.	Hamamoto-Kuroda, Ikuko (author) Properties unique in nuclei far from beta-stability line 2002 In: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 13, s. 21-21 Journal article (peer-reviewed)
30.	Hamamoto-Kuroda, Ikuko, et al. (author) Quantized wobbling excitations with alignments 2003 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:1: 014319 Journal article (peer-reviewed)abstract The wobbling excitations in the presence of an appreciable amount of alignment are expected to appear more easily at lower angular momenta of the yrast spectra, compared with those in the textbook example. The large B(E2;I-->I-1) value for Delta(n) over cap =1 transitions where (n) over cap expresses the number of wobbling phonons is shown to be a strongly increasing function of the triaxiality parameter gamma, especially for gammagreater than or similar to+20degrees, while it is relatively independent of moments of inertia. On the other hand, the relation of the wobbling phonon energy to the total angular momentum may be used to extract quantitative information on nuclear moments of inertia. It is concluded that the gamma value of the triaxial, strongly deformed bands in Lu-163 is about equal to +20degrees and may be slightly increasing as a function of I.
31.	Hamamoto-Kuroda, Ikuko, et al. (author) Quantized Wobbling in Nuclei 2003 In: Nuclear Physics News. ; 13:No.3, s. 20-20 Journal article (peer-reviewed)
32.	Hamamoto-Kuroda, Ikuko (author) Resonant and weakly-bound one-particle levels in quadrupole-deformed potentials 2007 In: The European Physical Journal. Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 150, s. 123-126 Journal article (peer-reviewed)
33.	Hamamoto-Kuroda, Ikuko (author) Selection Rule for Electromagnetic Transitions in Nuclear Chiral Geometry 2011 In: International Journal of Modern Physics E. - 0218-3013. ; 20:2, s. 373-379 Journal article (peer-reviewed)abstract In order to find the selection rules that can be applied to the electromagnetic transitions when the chiral geometry is achieved, a model for a special configuration in triaxial odd-odd nuclei is constructed which exhibits degenerate chiral bands with a sizable rotation. A quantum number obtained from the invariance of the Hamiltonian is given and the selection rule for electromagnetic transition probabilities in chiral bands is derived in terms of this quantum number. Among the available candidates for chiral bands of odd-odd nuclei, in which the near degeneracy of two Delta I = 1 bands is observed, the measured electromagnetic properties of the two bands in Cs-128(55)73 and Cs-126(55)71 are consistent with the rules, while those of Pr-134(59)75 and La-132(57)75 are not.
34.	Hamamoto-Kuroda, Ikuko, et al. (author) Self-consistent Hartree-Fock and RPA Green's function method indicate no pygmy resonance in the monopole response of neutron-rich Ni isotopes 2014 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:3 Journal article (peer-reviewed)abstract The random phase approximation (RPA) monopole strength and the unperturbed particle-hole excitation strength are studied, in which the strength in the continuum is properly treated without discretizing unbound particle spectra. The model is the self-consistent Hartree-Fock calculation and the RPA Green's function method with Skyrme interactions. Numerical examples are the Ni isotopes, especially Ni-68(28)40, in which an experimental observation of a low-lying peak with an appreciable amount of monopole strength at 12.9 +/- 1.0 MeV was recently reported. In the present study it is concluded that sharp monopole peaks with the width of the order of 1 MeV can hardly be expected for Ni-68 in that energy region. Instead, a broad shoulder of monopole strength consisting of neutron excitations to nonresonant one-particle states (called "threshold strength") with relatively low angular momenta (l, j) is obtained in the continuum energy region above the particle threshold, which is considerably lower than that of the isoscalar giant monopole resonance. In the case of monopole excitations of Ni-68 there are no unperturbed particle-hole states below 20 MeV, in which the particle expresses a neutron (or proton) resonant state. It is emphasized that in the theoretical estimate a proper treatment of the continuum is extremely important.
35.	Hamamoto-Kuroda, Ikuko (author) Shape, shell structure and collective modes unique to nuclei far from stability line 2002 In: Progress of Theoretical Physics Supplement. - 0375-9687. ; :146, s. 143-152 Conference paper (peer-reviewed)abstract The structure of nuclei far from beta-stability lines is expected to show various interesting and exotic phenomena, due to the unique features: (a) the presence of nucleons with very small binding energies and largely extended wave-functions; (b) large difference between the Fermi levels of protons and neutrons; (c) exotic ratios of the proton to neutron numbers for a given mass number. Among the topics, which are the direct consequence of those characteristic features and are being studied experimentally using the radioactive nuclear ion beam facilities in the world, I choose to talk about the one-particle shell-structure, response function, and related collective modes.
36.	Hamamoto-Kuroda, Ikuko (author) Shell-structure and pair-correlation in nuclei close to the neutron drip line 2004 In: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 731, s. 211-223 Journal article (peer-reviewed)abstract First, in the absence of pair correlation the properties of one-particle orbits of neutrons in nuclei close to the neutron drip line are briefly reviewed for both weakly bound neutrons and the neutrons in the continuum. The low-lying states in the continuum, which are close to the Fermi level, are of immediate importance for pair correlation and deformations of those nuclei. Then, the Hartree-Fock-Bogoliubov (HFB) equation in a simplified model is solved in coordinate space with the correct asymptotic boundary conditions, in order to provide quantitative characterization of both the role of weakly bound neutrons and the effect of the resonances in the continuum on pairing correlations.
37.	Hamamoto-Kuroda, Ikuko (author) Shell structure of one-particle resonances in deformed potentials 2016 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 93:5 Journal article (peer-reviewed)abstract The shell structure of low-lying neutron resonance levels in axially symmetric quadrupole-deformed potentials is discussed, which seems analogous to that of weakly bound neutrons. As numerical examples, nuclei slightly outside the neutron drip line, Mg271239 and C15621, are studied. For the lowest resonance I obtain Iπ=Ωπ=5/2- for Mg39 which is likely to be prolately deformed, while Iπ=Ωπ=1/2+ may be assigned to the nucleus C21 which may be oblately deformed. Consequently, C21 will not be observed as a recognizable resonance state, in agreement with the experimental information.
38.	Hamamoto-Kuroda, Ikuko (author) Shell structure of weakly-bound and resonant neutrons 2011 In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 267:1, s. 012005-012005 Conference paper (peer-reviewed)abstract The systematic change of shell structure in both weakly bound and resonant neutron one-particle levels in nuclei towards the neutron drip line is exhibited, solving the coupled equations derived from the Schrodinger equation in coordinate space with the correct asymptotic behaviour of wave functions for r -> infinity. The change comes from the behaviour unique in the one-particle motion with low orbital angular momenta compared with that with high orbital angular momenta. The observed deformation of very neutron-rich nuclei with N greater than or similar to 20 in the island of inversion is a natural result of this changed shell structure, while a possible deformation of neutron-drip-line nuclei with N approximate to 51, which are not yet observed, is suggested.
39.	Hamamoto-Kuroda, Ikuko (author) Two-phonon states in nuclei - From surface vibrations to wobbling motion 2003 In: Frontiers of Collective Motions (CM2002). - : WORLD SCIENTIFIC. - 9789812381989 ; , s. 376-386 Conference paper (peer-reviewed)abstract Being stimulated by the recent identification of the two-phonon wobbling excitation, first I make a brief survey of various two-phonon states in nuclear physics, in connection with experimental observations. Then, I discuss the wobbling-phonon excitation in the presence of particle alignments, which is nicely pinned down in the recent experiments of the nucleus Lu-163(71)92.
40.	Hamamoto-Kuroda, Ikuko, et al. (author) Weakly bound neutrons and quadrupole response function in the many-body pair correlation of neutron drip line nuclei 2006 In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 32:8, s. 1105-1119 Journal article (peer-reviewed)abstract A simplified model of the Hartree-Fock Bogoliubov (HFB) equation with surface-type or volume-type pairing is solved in coordinate space with the correct asymptotic boundary conditions. By using the resulting HFB wavefunctions, the low-energy quadrupole (L = 2) response function is studied for the system with weakly bound s and d neutrons. As the binding energy of the neutrons becomes small or approaches zero, the discrete solutions of the HFB equation disappear. Then, without any further correlation ( for example, random phase approximation ( RPA) correlation), the threshold quadrupole response becomes broader and moves toward very low excitation energies, while the total strength increases very rapidly. The important role of the continuum character of the upper component u(lj) (r) of the HFB s(1/2) wavefunction in the increasing strength is pointed out. The large and broad quadrupole response with a very low peak energy is expected for neutron drip line nuclei with N approximate to 56 and Z approximate to 28, of which both the neutron 2d(5/2) and 3s(1/2) orbits may be weakly bound in the Hartree-Fock (HF) potential.
41.	Hamamoto-Kuroda, Ikuko, et al. (author) Weakly-bound p3/2 neutrons and spin-response function in the many-body pair-correlation of neutron drip line nuclei 2004 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:3 Journal article (peer-reviewed)abstract Solving the simplified model of the Hartree-Fock Bogoliubov equation in coordinate space with the correct asymptotic boundary conditions, the spin-orbit splitting, occupation probabilities, effective pair-gap, mean square radius, and spin-response function are studied for weakly bound p neutrons. As the binding energy of p3∕2 neutrons becomes small or approaches zero, the spin-orbit splitting p3∕2−p1∕2 in the one-body potential drastically decreases and, at the same time, the effective pair-gap for the p neutrons becomes small, while the occupation probability of the p3∕2 level decreases only slightly. Consequently, in that limit low-lying broader spin response with almost constant amount of total strength appears with the peak moving toward very low excitation energies.
42.	Hamamoto-Kuroda, Ikuko, et al. (author) Weakly bound s(1/2) neutrons in the many-body pair correlation of neutron drip line nuclei 2004 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 69:6 Journal article (peer-reviewed)abstract With a simplified model in the Hartree-Fock-Bogoliubov (HFB) approximation, the behavior of weakly bound s(1/2) neutrons in the many-body pair correlation is studied by solving the HFB equation in coordinate space with the correct asymptotic boundary conditions. It is shown that in one-neutron pickup reactions on the even-even neutron-drip-line nuclei, which contain loosely bound s(1/2) neutrons, the strength of the s(1/2) neutron can appear both at a discrete state and in the low-energy continuum spectra, with comparable strength. When there is no weakly bound discrete state, the continuum spectra may exhibit a sharp peak just above E-x=lambda, which originates from the resonantlike behavior of the upper component of the HFB radial wave function, u(s1/2)(E-qp,r). This resonantlike behavior may be directly observed as an s-wave resonance close to E-x=/lambda in neutron-scattering experiments on those nuclei. It is also shown that a very large root-mean-square radius of loosely bound s(1/2) neutrons may appear also in the presence of many-body pair correlation, since the effective pair gap in weakly bound neutron orbits with low l values is much reduced.
43.	Hamamoto-Kuroda, Ikuko (author) Wobbling excitations in odd-A nuclei with high-j aligned particles 2002 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 65:4 Journal article (peer-reviewed)abstract Using the particle-rotor model in which one high-j quasiparticle is coupled to the core of triaxial shape, wobbling excitations are studied. The family of wobbling phonon excitations can be characterized by: (a) very similar intrinsic structure while collective rotation shows the wobbling feature; (b) strong B(E2;I-->I-1) values for Deltan(w)=1 transitions where n(w) expresses the number of wobbling phonons. For the Fermi level lying below the high-j shell with the most favorable triaxiality gammaapproximate to+20degrees, the wobbling phonon excitations may be more easily identified close to the yrast line, compared with the Fermi level lying around the middle of the shell with gammaapproximate to-30degrees. The spectroscopic study of the yrast states for the triaxial shape with -60degrees<γ<0 are illustrated by taking a representative example with gamma=-30degrees, in which a quantum number related with the special symmetry is introduced to help the physics understanding.
44.	Hartley, D. J., et al. (author) Wobbling mode in Ta-167 2009 In: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:4 Journal article (peer-reviewed)abstract The collective wobbling mode, the strongest signature for the rotation of a triaxial nucleus, has previously been seen only in a few Lu isotopes in spite of extensive searches in nearby isotopes. A sequence of transitions in the N = 94 Ta-167 nucleus exhibiting features similar to those attributed to the wobbling bands in the Lu nuclei has now been found. This band feeds into the pi i(13/2) band at a relative energy similar to that seen in the established wobbling bands and its dynamic moment of inertia and alignment properties are nearly identical to the i(13/2) structure over a significant frequency range. Given these characteristics, it is likely that the wobbling mode has been observed for the first time in a nucleus other than Lu, making this collective motion a more general phenomenon.
45.	Jensen, DR, et al. (author) Coexisting wobbling and quasiparticle excitations in the triaxial potential well of Lu-163 2004 In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 19:2, s. 173-185 Journal article (peer-reviewed)abstract High-spin states of the nucleus Lu-163 have been populated through the fusion-evaporation reaction La-139(Si-29, 5n) with a beam energy of 157 MeV. In addition to the two lowest excited triaxial strongly deformed (TSD) bands, recently interpreted as one- and two-phonon wobbling excitations, a third excited TSD band has been firmly established decaying to the yrast TSD band. The assignment of this band as a three-quasiparticle band shows together with the normal deformed (ND) level scheme the presence not only of shape coexistence between ND and TSD structures, but also an interplay of wobbling and quasiparticle excitations in the triaxial strongly deformed potential well of Lu-163.
46.	Jensen, DR, et al. (author) Evidence for second-phonon nuclear wobbling 2002 In: Physical Review Letters. - 1079-7114. ; 89:14 Journal article (peer-reviewed)abstract The nucleus Lu-163 has been populated through the reaction La-139(Si-29,5n) with a beam energy of 157 MeV. Three triaxial, strongly deformed (TSD) bands have been observed with very similar rotational properties. The first excited TSD band has earlier been assigned as a one-phonon wobbling excitation built on the lowest-lying (yrast) TSD band. The large B(E2)(out)/B(E2)(in) value obtainable for one of four observed transitions between the second and first excited TSD bands is in good agreement with particle-rotor calculations for a two-phonon wobbling excitation.
47.	Jensen, DR, et al. (author) Wobbling phonon excitations, coexisting with normal deformed structures in Lu-163 2002 In: Nuclear Physics, Section A. - 0375-9474. ; 703:1-2, s. 3-44 Journal article (peer-reviewed)abstract Wobbling is a rotational mode unique to a triaxial body. The Lu-Hf isotopes with N similar to 94 at high spin provide a possible region of nuclei with pronounced triaxiality. We have investigated Lu-163 through the fusion-evaporation reaction La-139(Si-29,5n)Lu-163 with a beam energy of 152 MeV. Three excited bands decaying into the known, presumably triaxial, superdeformed (TSD) band built on the i(13/2) proton orbital are observed. The electromagnetic properties of the connecting transitions from the two strongest populated excited TSD bands have been investigated. New particle-rotor calculations in which one i(13/2) quasiproton is coupled to the core of triaxial shape produce a variety of bands, whose properties can clearly be interpreted either as "wobbling" or "cranking" motion of the core. Evidence for the assignment of the excited TSD bands as one, and possibly even two wobbling phonon modes built on the yrast TSD band in Lu-163 is given. These triaxial bands coexist with bands built on quasiparticle excitations in the normal deformed (ND) minimum for which new data are also presented.
48.	Koike, T, et al. (author) Chiral bands, dynamical spontaneous symmetry breaking, and the selection rule for electromagnetic transitions in the chiral geometry 2004 In: Physical Review Letters. - 1079-7114. ; 93:17 Journal article (peer-reviewed)abstract A model for a special configuration in triaxial odd-odd nuclei is constructed which exhibits degenerate chiral bands with a sizable rotation, a manifestation of dynamical spontaneous symmetry breaking. A quantum number obtained from the invariance of the model Hamiltonian, which characterizes observable states, is given and selection rules for electromagnetic transition probabilities in chiral bands is derived in terms of this quantum number. The degeneracy of the lowest two bands is indeed obtained in the numerical diagonalization of the Hamiltonian at an intermediate spin range, over which electromagnetic transitions follow exactly the selection rule expected for the chiral geometry.
49.	Petrache, CM, et al. (author) Risk of misinterpretation of nearly degenerate pair bands as chiral partners in nuclei 2006 In: Physical Review Letters. - 1079-7114. ; 96:11 Journal article (peer-reviewed)abstract The experimental information on the observed nearly degenerate bands in the N = 75 isotones, in particular Pr-134 and Pm-136, which are often considered as the best candidates for chiral bands, is critically analyzed. Most properties of the bands, in particular, the recently measured branching ratios and lifetimes, are in clear disagreement with the interpretation of the two bands as chiral bands. For I = 14-18 in Pr-134, where the observed energies are almost degenerate, we have obtained a value of 2.0(4) for the ratio of the transition quadrupole moments of the two bands, which implies a considerable difference in the nuclear shape associated with the two bands. The insufficiency of the near-degeneracy criterion to trace nuclear chirality is emphasized.
50.	Shimbara, Y, et al. (author) Suppression of Gamow-Teller and M1 transitions in deformed mirror nuclei Mg-25 and Al-25 - Direct observation of K selection rules 2004 In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 19:1, s. 25-31 Journal article (peer-reviewed)abstract The mirror nuclei Mg-25 and Al-25 are expected to have very similar structures. The Gamow-Teller (GT) transitions from the J(pi) = 5/2(+) ground state of Mg-25 to the excited states in Al-25 were studied by high-resolution measurements of the Mg-25(He-3,t) charge-exchange reaction at 0degrees and at 140 MeV/nucleon. Assuming the usual DeltaJ(pi) = 1(+) selection rule for the spin-isospin-type GT transitions, the states with J(pi) = 3/2(+), 5/2(+), and 7/2 (+) should be excited. However, of the more than ten states with these J(pi) values below 6 MeV excitation energy, only the 5/2 (+) ground state and the 7/2 (+) , 1.613 MeV state in Al-25 were strongly populated, while all other states were strongly suppressed. The analysis of M1 transitions in Mg-25 also suggested a very similar feature for the analogous M1 transitions. Both Mg-25 and Al-25 are known to be largely deformed, and most low-lying states can be interpreted in terms of one-particle quantum numbers in the deformed potential and the associated rotational spectra. The observed suppression can be explained in terms of the K quantum number selection rules that are inherent to axially deformed nuclei.

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