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The $\ensuremath{\alpha}$ ($^{4}\mathrm{He}$)-clustering structure is a common phenomenon in light nuclei due to the decreasing contribution of the mean field in few-body systems. In this work, we presented calculations of giant dipole resonance (GDR) excitations for two non-$\ensuremath{\alpha}$-conjugate light nuclei, namely $^{6}\mathrm{Li}$ and $^{9}\mathrm{Be}$, within a framework of an extended quantum molecular dynamics model. For $^{6}\mathrm{Li}$, we investigated the GDR spectra from the two-body clustering structure with $\ensuremath{\alpha}\phantom{\rule{4pt}{0ex}}+$ deuteron as well as the three-body structure with $\ensuremath{\alpha}+n+p$, and found that the major $\ensuremath{\alpha}$-clustering contribution on the GDR peak is located at around 31 MeV, while the resonance contributions between clusters, namely $\ensuremath{\alpha}$ and deuteron or $(n+p)$, are located on the lower energy side, which can be regarded as the pygmy dipole resonance (PDR). For $^{9}\mathrm{Be}$, a mixture configuration contribution for the chain-like structure and Borromean-like structure of the $\ensuremath{\alpha}\phantom{\rule{4pt}{0ex}}+\phantom{\rule{4pt}{0ex}}n\phantom{\rule{4pt}{0ex}}+\phantom{\rule{4pt}{0ex}}\ensuremath{\alpha}$ configuration can explain its GDR results.

Low-energy dipole (LED) excitations in $^{18}\mathrm{O}$ were investigated using a combination of the variation after $K$ projection in the framework of antisymmetrized molecular dynamics with $\ensuremath{\beta}$ constraint with the generator coordinate method. We obtained two LED states, namely, the ${1}_{1}^{\ensuremath{-}}$ state with a dominant shell-model structure and the ${1}_{2}^{\ensuremath{-}}$ state with a large $^{14}\mathrm{C}+\ensuremath{\alpha}$ cluster component. Both these states had significant toroidal dipole (TD) and compressive dipole (CD) strengths, indicating that the TD and CD modes are not separated but mixed in the LED excitations of $^{18}\mathrm{O}$. This is unlike the CD and TD modes for well-deformed nuclei such as $^{10}\mathrm{Be}$, where the CD and TD modes are generated as ${K}^{\ensuremath{\pi}}={0}^{\ensuremath{-}}$ and ${K}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ excitations, respectively, in a largely deformed state.

This paper shows that a dipole close to a subwavelength sphere can give rise to an anapole, namely the dipole-scatterer is a non-radiating system. This state can be achieved with either a dielectric (high refractive index) or metallic particle.

Low-energy dipole excitations in ${}^{10}$Be were investigated based on the generator coordinate method with $\alpha + {}^6$He and $\alpha + \alpha + 2n$ cluster models. We obtained three $1^-$ states in $E_{x} < 15$~MeV, which show different characters in the $E1$, compressive dipole, and toroidal dipole transition strengths. We found the strong toroidal dipole transition in the $1_1^-$ state, remarkable $E1$ strength in the $1^-_2$ state, and the strong $E1$ and compressive dipole strength in the $1^-_3$ state. The $1^-_1$ is described by the $\alpha + {}^6$He cluster structure, where as the $1^-_2$ and $1^-_3$ states are understood by three-body excitations of the $\alpha + \alpha + 2n$ clustering., Comment: 20 pages, 8 figures

Due to the utilization of overlapped dipole resonances, traditional Huygens’ metasurfaces suffer from dipole interactions. In this Letter, we propose a design of phase-gradient Huygens’ metasurface based on the quadrupole resonances excited in the cross-shaped structures. The quadrupole resonances are theoretically shown insensitive to the quadrupole interactions. Benefiting from this intrinsic property, the proposed metasurface can well suppress element interaction influence and exhibits some impressive properties, including the ability to suppress high diffraction orders, tunable anomalous refractive angles, and high transmission efficiency. The numerical results show promising potential for quadrupole resonances to be applied in advanced Huygens’ metasurface designs.

The low-energy behavior of the strength function for the $1^-$ soft dipole excitation in $^{6}$He is studied theoretically. Use of very large basis sizes and well-grounded extrapolation procedures allows to move to energies as small as 1 keV, at which the low-energy asymptotic behavior of the E1 strength function seems to be achieved. It is found that the low-energy behavior of the strength function is well described in the effective three-body "dynamical dineutron model". The astrophysical rate for the $\alpha$+$n$+$n \rightarrow ^6$He+$\gamma$ is calculated. Comparison with the previous calculations is performed., Comment: 6 pages, 9 figures

We investigate tensor effects in pygmy dipole excitations for the case of neutron-rich nuclei 68 Ni and 124 Sn using effective nucleon–nucleon Skyrme interaction. We use the Hartree–Fock–Bogoliubov (HFB) theory and employ the quasiparticle random phase approximation (QRPA). We calculate and compare the PDR and also GDR strength in the PDR–GDR energy region for QRPA calculations with and without tensor correlations. The most obvious results for the dipole excitations calculations are strongly dependent on the tensor terms. We see that the tensor correlations are more active at around 14–20 MeV , especially for the neutron-rich nuclei 68 Ni . We also compare the PDR calculations with their experimental results for the different proton–neutron tensor coupling constants.

We investigate isovector pygmy dipole resonance (IVPDR) for the case of neutron-rich nuclei 68 Ni , 130 Sn and 134 Sn using effective nucleon–nucleon Skyrme interaction. We use the Hartree–Fock–Bogoliubov (HFB) theory and employ the (quasiparticle) random phase approximation (Q)RPA. We calculate and compare the PDR strength in the PDR energy region for the case of density dependent central and full interaction modes for RPA and QRPA calculations. We observe that the results for the pygmy dipole resonance for neutron-rich soft nuclei 68 Ni that we consider are in reasonable agreement with their experimental results in both interactions and calculations. We also study the PDR for highly neutron-rich heavy nuclei, such as 130 Sn and 134 Sn . We see that only the QRPA calculation with full interaction is in good agreement with the experimental results for these nuclei and with a recent study in the literature. We find that the PDR strength distribution sensitively depends on the chosen interaction modes, especially for the neutron-rich heavy nuclei 134 Sn .

Using a three-body model with density-dependent contact interaction, we discuss the role of dineutron correlation in the ground state properties as well as in the dipole excitation of typical weakly-bound Borromean nuclei, 11 Li and 6 He . We show that, while both the nuclei manifest themselves similar strong dineutron correlations to each other in the ground state, the energy distributions for the two emitted neutrons from the dipole excitation are considerably different. We also discuss briefly the diproton correlation in a proton-rich Borromean nucleus, 17 Ne .

Thanks to the experimental breakthrough of the last years in the manipulation of ultra cold atomic gases, it has become possible to realize low-dimensional and mesoscopic quantum fluids. The object of this thesis is the theoretical investigation of a few mesoscopic systems that can be realized with a one-dimensional Bose gas. These systems exhibit interesting quantum phenomena, and are potentially relevant for technological applications. We study the phenomenon of persistent currents induced by stirring the gas confined on a ring with a potential barrier, we examine the feasibility of a qubit based on the superposition of current states in a ring lattice threaded by a gauge field in the presence of a weak-link, and we investigate the dipole excitation of the gas in a split trap induced by an out-of-equilibrium displacement of the external potential. In all these cases, we apply a combination of analytical and numerical approaches that allow to cover all the interaction regimes. As a recurring theme, we disclose a so-far unknown regime of maximal screening of the barrier potential by the fluid, arising from the interplay of effects due to interactions and quantum fluctuations. These results have significant consequences for the behaviour of such systems and are important for the ongoing and future realization of ultracold atomic gases devices.; Ces dernières années d'importantes avancées techniques dans la manipulation des gaz atomiques ultrafroids ont ouvert la voie à la réalisation de fluides quantiques mésoscopiques de basse dimension. L'objet de cette thèse est l'étude théorique de certains systèmes mésoscopiques réalisables avec un gaz de Bose unidimensionel. Ces systèmes présentent des phénomènes quantiques intéressants, et sont potentiellement utiles en vue d'applications technologiques. Nous étudions le phénomène des courants permanents induits dans un gaz confiné sur un anneau par la rotation d'une barrière de potentiel, nous examinons la faisabilité d'un qubit fondé sur la superposition d'états de courant dans un réseau en forme d'anneau traversé par un champ de jauge et contenant un 'weak-link', ainsi que l'excitation dipolaire du gaz dans un 'split-trap' induit par le déplacement hors équilibre du potentiel externe. Dans tous ces cas, nous combinons diverses approches analytiques et numériques, qui permettent de couvrir l'ensemble des régimes d'interactions. Nous mettons en lumière un régime jusque-là inconnu, d'écrantage maximal des barrières de potentiel par le fluide, dû à une competition entre les effets des interactions et des fluctuations quantiques. Ces résultats ont des conséquences significatives sur le comportement de tels systèmes et, de ce fait, sont importants pour les réalisations en cours et à venir de dispositifs à gaz d'atomes ultrafroids.

We investigate the effects of the long-range dynamic polarization (LRDP) potential, which consists of the Coulomb dipole excitation (CDE) potential and the long-range nuclear (LRN) potential, for the $^{11}\mathrm{Be}$ projectile on $^{64}\mathrm{Zn}$. To study these effects, we perform a ${\ensuremath{\chi}}^{2}$ analysis of an optical model including the LRDP potential as well as a conventional short-range nuclear (SRN) potential. To take these effects into account, we argue that both the CDE and LRN potentials are essential to explaining the experimental values of ${P}_{E}$, which is the ratio of the elastic scattering cross section to the Rutherford cross section. The Coulomb and nuclear parts of the LRDP potential are found to contribute to a strong absorption effect. Strong absorption occurs because the real part of the CDE and LRN potentials lowers the barrier, and the imaginary part of the CDE and LRN potentials removes the flux from the elastic channel in the $^{11}\mathrm{Be}+^{64}\mathrm{Zn}$ system. Finally, we extract the total reaction cross section ${\ensuremath{\sigma}}_{R}$ including the inelastic, breakup, and fusion cross sections. The contribution of the inelastic scattering by the first excited state at ${\ensuremath{\varepsilon}}_{\mathrm{x}}^{1\mathrm{st}}=0.32\phantom{\rule{4pt}{0ex}}\mathrm{MeV}\phantom{\rule{4pt}{0ex}}(1/{2}^{\ensuremath{-}})$ is found to be relatively large and cannot be ignored. In addition, our results are shown to agree quite well with the experimental breakup reaction cross section by using a fairly large radius parameter.

Generally speaking, charged-particle traps are devices which achieve the confinement of charged subatomic, atomic or molecular particles in a finite volume of space, through a combination of electric and magnetic fields (which can be static or dynamic) [Maj05]. Due to their wide range of applications, charged-particle traps have become key components of experimental-physics facilities today [Wer09].

We investigate the effects of long-range dynamic polarization on elastic cross sections for heavy-ion collisions which comprise the Coulomb dipole excitation (CDE) potential and the long-range nuclear (LRN) potential. To study these effects, we perform a ${\ensuremath{\chi}}^{2}$ analysis for the elastic cross sections of $^{11}\mathrm{Li}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}^{208}\mathrm{Pb}$ and $^{6}\mathrm{He}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}^{208}\mathrm{Pb}$ systems using the long-range dynamic polarization potentials. For the CDE we formulate some empirical models to reproduce the experimental Coulomb dipole strength $B(E1)$ distribution and apply to the collision of $^{11}\mathrm{Li}$ and $^{6}\mathrm{He}$. But the CDE potential turns out to be not enough to explain the experimental data relevant to the nuclei. It leads us to additionally take the LRN potential peculiar to these halo nuclei into account. Our model, which was constructed by adding the CDE and LRN potentials to the conventional short-range nuclear potential corrected by the Coulomb interaction, provides a good description of the experimental data. In particular, the surface type is shown to be more reasonable rather than the volume type in the LRN potential.

Science is—as emphasized 50 years ago by Thomas Kuhn in his academic bestseller The Structure of Scientific Revolutions—driven by paradigms, rooted in outstanding discoveries and practice. At the centennial for the nuclear atom, it may be appropriate to address the current paradigmatic situation for nuclear physics on background of the large investments made during the last decades. Following Rutherford’s paradigm, nuclear physics has developed by colliding nuclei and from studying the fragments that emerge. With restriction to new forms of transient cold nuclear matter, we will address if and how new discoveries have influenced the way we think about nuclear architecture, drawing parallels with comparable development in other branches of science. Recent discoveries in halo nuclei, \(^{11}\)Be and the Borromean \(^{22}\)C will serve as our cardinal examples. The challenges at driplines may appear less dramatic than what calls for a Kuhnian turnover, still we hope to convey that valuable lessons may be learned. The attention-grabbing dripline lessons we address are rooted in emergent degrees of freedom involving cluster constituents. This is a great challenge for the ruling paradigm, a shell-model inspired ab initio nucleon-based theory, developed and tested for stable nuclei, and currently being tuned to encompass dripline lessons. Our mental pictures and dynamic understanding of many of the outstanding dripline phenomena will, however, remain linked to cluster degrees of freedom. This duality makes our paradigmatic lessons conceptually less dramatic than what Kuhn’s “incommensurability” may imply.

For the $^{11}\mathrm{Li}+^{208}\mathrm{Pb}$ system, we find that the breakup process takes place from the forward angle or far distance region through the interaction distance which is obtained from ratios of elastic scattering cross sections to the Rutherford cross section. It is well known that the behavior of the $^{11}\mathrm{Li}+^{208}\mathrm{Pb}$ system is closely related to Coulomb dipole excitation effect. From the first ${\ensuremath{\chi}}^{2}$ analysis for the elastic cross section of the $^{9}\mathrm{Li}+^{208}\mathrm{Pb}$ system, we obtain the short-range potential of the $^{11}\mathrm{Li}+^{208}\mathrm{Pb}$ system by exploiting the optical model calculation for the Coulomb dipole excitation effect. To include the effect of the long-range interaction, we use a dynamic complex polarization potential including the Coulomb dipole potential and a long-range nuclear potential with Woods-Saxon form. Using the second ${\ensuremath{\chi}}^{2}$ analysis for the elastic cross section of the $^{11}\mathrm{Li}+^{208}\mathrm{Pb}$ system, we obtain the electric dipole transition probabilities $B(E1)$ which becomes 1.42 ${e}^{2}{\mathrm{fm}}^{2}$ and 1.41 ${e}^{2}{\mathrm{fm}}^{2}$ at ${E}_{\mathrm{c}.\mathrm{m}.}$ = 23.1 MeV and 28.3 MeV, respectively.

Vibrational states built on the K π = 9− isomer and on the ground state (K π = 1+) in 180Ta are calculated within the quasiparticle-phonon nuclear model using the 178Hf nucleus as a core. A procedure for calculating the rates of K-allowed γ-ray transitions from vibrational states built on the isomer to those built on the ground state is presented. The probabilities of two-step processes consisting of a dipole excitation of the isomer and successive E1 and E2 transitions from them to vibrational states built on the ground state of the 180Ta nucleus are calculated. Two-step transitions from the isomer to vibrational states below 2.7 MeV and to the vibrational states built on the ground state appear to be very weak. There are many E1 transitions from the vibrational states built on the isomer to the vibrational states built on the ground state. They are weak and cannot be responsible for the strong deexcitation of 180m Ta in the relevant (γ, γ′) reaction. A decisive role is played by collective E2 transitions from dipole excitations in several excitation energy intervals ranging between 2.7 and 4.0 MeV. These highly intense K-allowed two-step γ-ray transitions can be responsible for the strong deexcitation of the 180m Ta state in the (γ, γ′) reactions.

Properties of positronium (Ps), its negative ion, and the recently discovered positronium molecule are briefly reviewed. Emphasis is on the recent progress and on quantities of current experimental interest, including the Ps atomic and molecular spectrum, and the ion lifetime.

Cross-sections for dipole excitation of low energy (0.1–0.3 eV) electron–hole pairs at the (111) and (100) surfaces of aluminium have been measured with use of electron energy loss spectroscopy. We observe a substantial crystal-face effect at low incident electron energies (

A recently proposed fluctuation analysis of resonant photon scattering spectra [J. Enders et al., Phys. Rev. Lett. 79, 2010 (1997)] is applied to the ${}^{157}\mathrm{Gd}(\ensuremath{\gamma},{\ensuremath{\gamma}}^{\ensuremath{'}})$ reaction. Evidence for unresolved strength in the experimental background is found which amounts to a total dipole excitation strength of $\ensuremath{\sum}g{\ensuremath{\Gamma}}_{0}^{\mathrm{red}}{=(30}_{\ensuremath{-}10}^{+6}){\mathrm{m}\mathrm{e}\mathrm{V}/\mathrm{M}\mathrm{e}\mathrm{V}}^{3}$ in the excitation energy range 2.5--4 MeV. Assuming a smooth variation of the $M1/E1$ strength ratio in the neighboring even-mass nuclei, the $M1$ part can be estimated to be ${B(M1)=(2.0}_{\ensuremath{-}0.7}^{+0.4})$ ${\ensuremath{\mu}}_{N}^{2}.$ This value is close to the expectation of sum rules. We discuss possible sources of errors which suggests that the obtained value represents a lower limit only.

A photon scattering experiment was performed on the $\ensuremath{\gamma}$-soft nucleus $^{134}\mathrm{Ba}$ with photon energies of ${E}_{\ensuremath{\gamma}}l4.1$. Around 3 MeV excitation energy a fragmented ${1}^{+}$ scissors mode as well as the ${({2}^{+}\ensuremath{\bigotimes}{3}^{\ensuremath{-}})}_{{1}^{\ensuremath{-}}}$ two-phonon dipole state were identified. The dipole excitation strengths were measured. The excitation strength of the scissors mode in this $\ensuremath{\gamma}$-soft nucleus is well reproduced by an empirical $M1$ sum rule that generalizes the "${\ensuremath{\delta}}^{2}$ law" to nuclei without axial symmetry. The IBM-2 describes the mixed-symmetry states in $^{134}\mathrm{Ba}$ and their decay pattern. A large $\frac{E2}{M1}$ mixing ratio for the ${1}^{+}$\ensuremath{\rightarrow}${2}_{1}^{+}$ decay of the scissors mode to the ${2}_{1}^{+}$ state is predicted by the IBM-2. The new result from $^{134}\mathrm{Ba}$ together with a similar previous observation in $^{196}\mathrm{Pt}$ corroborates the scissors mode as a typical excitation mode of $\ensuremath{\gamma}$-soft nuclei.

Resonant inelastic proton scattering experiments were carried out to investigate the {gamma} decay of the 1{sup {minus}} state at an excitation energy of around 3.5 MeV in the {ital N}=82 nuclei {sup 142}Nd and {sup 144}Sm. {gamma}-ray branching ratios were determined from {gamma}-proton coincidences in both nuclei. The newly observed {gamma} decay of the dipole excitation at 3225 keV in {sup 144}Sm to the one-phonon states, in particular the (1{sup {minus}}{r_arrow}3{sub 1}{sup {minus}}) {ital E}2 transition to the octupole phonon state, is the first direct proof of the two-phonon character of the 1{sup {minus}} state in any {ital N}=82 nucleus. {copyright} {ital 1996 The American Physical Society.}

Highlights of RIKEN radioactive beam experiments are reviewed. In particular the phenomena of giant soft dipole excitation of halo nuclei are closely discussed.

Coulomb excitations using radioactive beams are discussed. Applications of such reactions are described including soft dipole excitation of neutron halo nuclei, collective E2 excitation of 32 Mg and astrophysically interesting 8 B breakup.

By using the hybrid- TV model of the 4 He + n + n three-body system, the binding energy and excited states of "He are investigated. The binding energy 0.784 MeV is obtained for more realistic 4 He-n interaction. It is discussed that the n-n correlations, which are fully taken into account in the ECM bases, are very important to reproduce the binding energy of "He. The excited resonance states of the "He system are also calculated by applying the complex scaling method. The first excited z+ state obtained as a three-body resonance state is in good agreement with experiments. However, the excited 1- resonance states corresponding to the soft dipole excitation are not obtained at the low energy region.

A general method for the calculation of second order effects in the Coulomb dissociation is presented in the small ξ-limit avoiding the introduction of intermediate states. The amplitudes for a dipole excitation are analytically calculated in a simple model for the projectile with a zero-range force. The model is applied to the excitation of 11 Li at projectile energies of 28 and 800 MeV nucleon . The angular and energy distribution of the fragments and post-acceleration effects are examined in first and second order perturbation theory as well as the sudden approximation.

Cross sections for the electromagnetic dissociation of 197 Au targets by 1.7 A GeV 20 Ne and 1 A GeV 88 Kr, 197 Au and 209 Bi beams have been measured by an activation method. Weizsacker-Williams calculations show that the experimental 1n cross sections can be understood by first order excitation of the giant dipole and the isoscalar giant quadrupole resonance. In contrast, the 3n cross sections show a much stronger Z proj - dependence, which can only be explained by a dominant contribution from two-phonon giant dipole excitation.

The GTEM (GigaTEM) cell is proving a useful tool for characterizing the EM emission of objects under laboratory conditions. In order to enhance its practical use, however, it is essential to be able to identify and predict differences between tests in "open site" and in cell environment. The modes of the empty cell were previously reported. In this contribution, we address in the first time the problem of excitation by dipoles in the non uniform environment of the cell. Moreover, we present an analytical model of the scattering by a dielectric or conducting sphere in the cell. Numerical results are compared with experimental data, when possible, and with theoretical results for scattering by the same object in free space, showing very good agreement as regards the resonant frequencies. >