Quadrupole Excitations Research Articles

Ultrahigh Q surface lattice resonance supported by a U-shaped resonant ring nanoarray.

We achieved an ultrahigh Q surface lattice resonance (SLR) using a conventional U-shaped split ring resonator (U-SRR) array. Numerical results confirmed by semi-analytical analysis show that with the transmission resonance amplitude up to 0.8, the Q-factor of the SLR can still surpass 104. The physical mechanisms of the ultrahigh Q-factor were also investigated. Besides the radiation suppression provided by conventional SLR, the unique geometry of the U-SRR can further offer dual radiation suppression mechanisms: reduction of the dipole moment and excitation of the in-plane quadrupole. We expect that the proposed ultrahigh Q SLR platform will be explored for more flexible and advanced nanoscale devices.

A simple numerical simulation model can elucidate the key factors for designing a miniaturized ion trap mass spectrometer

BackgroundMiniature ion trap mass spectrometer enables mass-to-charge ratio analysis of ions via quadrupole field in a low vacuum environment. It plays an important role in on-site detection due to its portability and specificity. In order to gain a deeper understanding of the analysis mechanism of miniature ion trap mass spectrometers, a quadrupole MS ion trajectory numerical simulation model (QITNS) is established in this paper for ions trajectory calculation under the action of quadrupole field, exciting field and neutral gas molecule collision. Compared with the existing methods, the model in this paper is simpler and more direct, which effectively explored the effects of dipole excitation and quadrupole excitation on ion manipulation under high background pressure. ResultsThe simulation results demonstrate that high RF amplitude, low auxiliary AC amplitude and quadrupole excitation can effectively improve the isolation resolution. Besides, it clarified the difference between the analysis mechanism of ion trap mass spectrometers under high background pressure (above 13.332 Pa) and absolute vacuum conditions. The relevant results are consistent with the conclusions of previous experiments and other theories, proving the applicability and accuracy of the proposed calculation model and solution method. SignificanceThis research bears the guiding significance for further understanding the mechanism of quadrupole mass spectrometry as well as designing and developing miniature mass spectrometers.

Research on double resonant excitation in a triangular electrode ion trap with asymmetric geometry.

The triangular electrode linear ion trap with asymmetric geometry has been reported to possess a high ion unidirectional ejection efficiency and a reasonable mass resolution. To further improve its performance, a double resonant excitation method involving a dipolar and a quadrupolar resonant excitation was applied here. The dipolar excitation method was carried out by applying a supplementary alternating voltage out of phase to one pair of the electrodes, whereas the quadrupolar excitation (QE) method was carried out by adding a supplementary alternating voltage in phase to another pair of electrodes. Numerical simulations were performed to explore the impact of the frequency difference between the alternating current (AC) and the QE voltage (∆ω), the frequency of the AC voltage (ωAC), and the QE voltage amplitude (VQE). The mass resolution could be improved to ~4700 , which was approximately twice compared to that with only dipolar resonant excitation, and the ion unidirectional ejection efficiency could be improved to 97%. Even with a high scan rate of 6000 Da/s, there was minimal loss of mass resolution caused by increased scan rate in double resonant excitation mode. By employing the double resonant excitation method, the mass resolution could be further increased while maintaining a considerably high ion unidirectional ejection efficiency, which might be a simple and practical approach for developing a high-performance miniature ion trap mass analyzer.

Quadrupole excitation of atoms with tightly focused Laguerre-Gaussian beams.

This article investigates the quadrupole excitation of a trapped atom exposed to the tightly focused Laguerre-Gaussian (LG) beams with parallel and antiparallel spin angular momentum (SAM) and orbital angular momentum (OAM) under nonparaxial conditions. The Rabi frequency profile of allowed quadrupole transition channels, modified by SAM and OAM interaction, in the focal plane is provided. In the case of antiparallel SAM and OAM, the excitation probability undergoes substantial modification due to the considerable contribution of longitudinal intensity variations in tightly focused condition. The findings offer insights into controlling localized atom transition, including OAM transfer, with potential applications in qudit-based technologies.

Inelastic scattering reaction as a probe for monopole, dipole and quadrupole excitations

The study of collective motions within atomic nuclei, such as monopole, dipole, and quadrupole excitations, is crucial for understanding nuclear structure and properties, which provide insights into the spatial distribution and dynamic nature of protons and neutrons in nuclei. By analyzing the angular distributions of these modes excited via inelastic scattering reactions, we can determine the transition characteristics and deformation lengths of nuclei. Specific case studies, including quadrupole excitations and dipole excitations indicating exotic cluster structures in light nuclei, highlight the utility of modern experimental setups like the solenoidal spectrometer and the active target detector.

Prospect for precision quantum logic spectroscopy of vibrational overtone transitions in molecular oxygen ions

Precision spectroscopy has been the driving force for progress of our physical understanding and still is a promising tool for the investigation of new physics. Molecules offer transitions which allow tests that are not possible in atomic systems. However, usually precision spectroscopy of molecules is challenging due to the lack of cycling transitions for state preparation and state detection. For molecular ions, this obstacle can be overcome by quantum logic spectroscopy, where dissipation for state preparation and detection is provided by a co-trapped atomic ion exploiting the shared eigenstates of motion. Here, we propose a full quantum logic spectroscopy scheme for molecular oxygen ions and theoretically investigate the feasibility of quantum logic-assisted state detection and preparation. Furthermore, we provide coupling rates for a direct single-photon quadrupole excitation of a vibrational overtone transition that can serve as a sensitive reference for tests of a possible variation of the proton-to-electron mass ratio.

The measurement of the E2 nuclear resonance effects in kaonic atoms at DAΦNE: The KAMEO proposal

KAMEO (Kaonic Atoms Measuring Nuclear Resonance Effects Ob-servables) is a proposal for an experiment aiming to perform the first consistent measurement of the E2 nuclear resonance effects in kaonic molybdenum A=94,96,98,100 isotopes. The E2 nuclear resonance mixes atomic states, due to the electrical quadrupole excitation of nuclear rotational states. It occurs in atoms having the energy of a nuclear excitation state closely matching an atomic de-excitation state energy, and affects the rates of X-ray atomic transitions matching the energy of the resonance. The measurement E2 nuclear resonance effect in KMO isotopes allows the study of the strong kaon-nucleus interaction in a rotational excited nuclear state. Moreover, the effect enables the K- to access an inner atomic level not easily reachable by the kaon normal cascade, due to the nuclear absorption. The KAMEO proposed apparatus consists of 4 enriched Mo A=94,96,98,100 isotope strips, exposed to the kaons produced by the DAφNE collider, for kaonic atoms formation, with a high-purity germanium detector, cooled with liquid nitrogen, used to measure the X-ray atomic transitions. The DAφNE collider is located at the National Laboratories of Frascati (LNF-INFN), in Italy. It is already suited for kaonic atoms measurement by the SIDDHARTA-2 collaboration.

Observation of Magnetic Quadrupole Endowed Helical Dichroism in Artificial Propeller Meta‐Molecules

AbstractThis study demonstrates that the magnetic quadrupole (MQ) can make an indispensable contribution to helical dichroism (HD), which is distinct from HD caused by electric quadrupole (EQ). Specifically, the established multipole expansion theory of the light–matter interaction reveals that EQ‐induced HD belongs to the pure electric dipole–quadrupole (E1‐E2) excitation, while newly discovered MQ‐induced HD belongs to the pure magnetic dipole‐quadrupole (M1‐M2) excitation. Metallic propeller meta‐molecules are used to elaborate on this novel physical mechanism and demonstrate that HD can be significantly enhanced and flexibly tuned by increasing stereo twist of propeller meta‐molecules or slightly focusing the linearly polarized vortex beam to improve the orbital angular momentum number. Importantly, the aforementioned intriguing phenomena are validated by fabricating stereo twisted propeller meta‐molecules via nano‐kirigami method. The findings reveal a paradigm‐shift approach to manipulate the chiroptical response of a single metallic nanostructure via photonic orbital angular moment, opening prospects for optical encryption, communication, next‐generation chiroptical spectroscopy, and chiral vortex optical devices.

Dipole and quadrupole resonance excitation in linear quadrupoles.

In the development of commercial quadrupole mass spectrometers, there is an interest in improving the performance characteristics such as transmission, resolution, and mass range. In particular, parametric and dipolar resonance excitation of trapping ions are used for linear quadrupole mass filters. Theoretical methods and numerical simulation of ion trajectories were applied for study of ion-optical properties. The review is devoted to description of different excitation methods to improve QMF performance and consists of three parts. The first part presents the results of a linear ion trap simulation for various operating conditions and excitation methods. The second part considers the effects of dipole excitation (DE) on the performance of the quadrupole mass filter. The last part analyzes the formation of stability islands by different methods of quadrupole excitation. To date conditions of mass separation in quadrupole mass filters with sin wave supply were described for stability islands of the first and third stability regions formed by quadrupole and DE. By complicating the electronics such methods allow to overcome the destructive influence of electric field distortions and obtain a resolving power and ion transmission efficiency comparable with commercial devices. At quadrupole resonance excitation by a two-frequency signal, it is possible to reduce the length of electrodes three times without losses in resolution and transmission, which reduces the cost of rod set production with micrometer accuracy. Dipole resonance excitation allows controlling the shape of the mass peak by changing amplitude and phase of the auxiliary AC signal. The main factors affecting the resolving power of a linear ion trap are described theoretically. The numerical modeling results are confirmed by experiment.

Superlattice Surface Lattice Resonances in Plasmonic Nanoparticle Arrays with Patterned Dielectrics.

This paper describes how two-dimensional plasmonic nanoparticle lattices covered with microscale arrays of dielectric patches can show superlattice surface lattice resonances (SLRs). These optical resonances originate from multiscale diffractive coupling that can be controlled by the periodicity and size of the patterned dielectrics. The features in the optical dispersion diagram are similar to those of index-matched microscale arrays of metal nanoparticle lattices, having the same lateral dimensions as the dielectric patches. With an increase in nanoparticle size, superlattice SLRs can also support quadrupole excitations with distinct dispersion diagrams. The tunable optical band structure enabled by patterned dielectrics on plasmonic nanoparticle arrays offers prospects for enhanced nonlinear optics, nanoscale lasing, and engineered parity-time symmetries.

Theory of plasmon-polaritons in binary metallic supercrystals

We present a theory of optical excitations in binary plasmonic supercrystals that are made out of two types of metal nanoparticles. Compared to monodisperse supercrystals, binary crystals have a larger number of plasmonic bands. Their dispersion is governed by the lattice symmetry, unit cell parameters, and shape and material composition of the nanoparticle building blocks. We develop a quantum description of the plasmon polaritons in supercrystals that starts from the dipole and quadrupole excitations of the nanoparticles, their interaction, and their coupling to photons. We show how to use group theory to analyze the plasmon- and photon-induced supercrystal states and their interaction. Plasmon-polaritons of binary metallic supercrystals are in the regime of ultrastrong and deep strong light-matter interaction; i.e., the coupling strength is on the same order as the photon energy. One consequence of the strong interaction is that quadrupolar plasmon modes and photons with energies well above the plasmon energies have to be taken into account to calculate the polariton dispersion. A cesium chloride crystal of two nanoparticles with different dipole and quadrupole energies serves as the example structure to show how the plasmon-polariton dispersion depends on the properties of the nanoparticles and supercrystal structure. The tools presented here can be used to predict and analyze any type of optically active excitation in supercrystals. The results show how to differentiate the optical properties of binary nanoparticle supercrystals into properties that inflexibly depend on lattice symmetry and properties that can be finely tuned by choosing the nanoparticle composition and shape.

Study of S, Cl and Ar isotopes with $$N \ge Z$$ using microscopic effective sd-shell interactions

In the present work, newly developed microscopic effective $sd$-valence shell interactions such as chiral next-to-next-to-next-to-leading order (N3LO), $J$-matrix inverse scattering potential (JISP16), Daejeon16 (DJ16), and monopole-modified DJ16 (DJ16A) are employed to study the nuclear structural properties of sulphur, chlorine, and argon isotopes with $N \geq Z$. These interactions are derived using the \textit{ab initio} no-core shell-model and the OLS unitary transformation method. We calculate energy spectra and electromagnetic properties to test the predictive strength of the effective interactions for these heavier $sd$-shell nuclei. For a complete systematic study, we compare the microscopic results with the phenomenological USDB results and experimental data. By looking at the excitation energies of these nuclei, the DJ16A interaction is found to be {the} most suitable for these $sd$-shell nuclei among all microscopic interactions. The electric quadrupole transition strength and excitation energy of the first $2^+$ state data of even-even sulphur isotopes indicate the presence of the $N=20$ shell closure. Quadrupole moment predictions are also made using these interactions where experimental data are unknown. Magnetic moments are in excellent agreement with the experimental values. The root-mean-square deviations are also calculated to provide an idea of how accurate the interactions are.

Magnetic quadrupole transitions in the relativistic energy density functional theory

Magnetic quadrupole (M2) excitation represents a fundamental feature in atomic nucleus associated to nuclear magnetism induced by spin and orbital transition operator. Since it has only been investigated within the non-relativistic theoretical approaches, and available experimental data are rather limited, it is interesting to study the properties of M2 transitions using the framework of relativistic nuclear energy density functional. In this work the nuclear ground state is calculated with relativistic Hartree-Bogoliubov model, while the M2 excitations are described using the relativistic quasiparticle random phase approximation with the residual interaction extended with the isovector-pseudovector term. The M2 transition strength distributions are described and analyzed for closed shell nuclei $$^{16}$$ O, $$^{48}$$ Ca, $$^{208}$$ Pb, open-shell $$^{18} \mathrm O$$ , $$^{42}$$ Ca, $$^{56}$$ Fe, and semi-magic $$^{90}$$ Zr. The evolution of M2 transition properties has been investigated within the $$^{36-64} \mathrm Ca$$ isotope chain. The main M2 transitions have rather rich underlying structure and detailed analysis shows that collectivity increases with the mass number due to larger number of contributing particle-hole configurations. Pairing correlations in open shell nuclei have strong effect, causing the reduction of M2 strength and shifts of the centroid energies to higher values. The analysis of M2 transition strengths indicate that considerable amount of experimental strength may be missing, mainly due to limitations to rather restricted energy ranges. The calculated M2 strengths for Ca isotopes, together with the future experimental data will allow constraining the quenching of the g factors in nuclear medium.

Correlation of Neutrinoless Double-β Decay Nuclear Matrix Element with E2 Strength

We explore the correlation of the neutrinoless double-β decay nuclear matrix element (NME) with electric quadrupole (E2) strength in the framework of the Hamiltonian-based generator-coordinate method, which is a configuration-mixing calculation of symmetry-restored intrinsic basis states. The restoration of symmetries that are simultaneously broken in the mean-field states allows us to compute the structural and decay properties associated with wave functions characterized by good quantum numbers. Our calculations show a clear anti-correlation between the neutrinoless double-β decay NME and the transition rate of the collective quadrupole excitation from the ground state in response to artificial changes of the quadrupole–quadrupole interaction. The anti-correlation is more remarkable in the decay from a weakly deformed parent nucleus to a more deformed grand-daughter nucleus. This interrelation may provide a way to reduce the uncertainty of the nuclear matrix element.

Isolated-core quadrupole excitation of highly excited autoionizing Rydberg states

The structure and photoexcitation dynamics of high lying doubly excited states of the strontium atom with high angular momenta are studied in the vicinity of the Sr$^+(N=5)$ threshold. The spectra recorded using resonant multiphoton isolated core excitation are analyzed with calculations based on configuration interaction with exterior complex scaling, which treats the correlated motion of the two valence electrons of Sr from first principles. The results are rationalized with a model based on multichannel quantum-defect theory and transition dipole moments calculated with a perturbative treatment of electron correlations. Together, both approaches reveal that most of the lines observed in the spectra arise from the interaction of a single optically active state, coupled to the initial state by an electric-dipole transition, with entire doubly-excited Rydberg series. The long-range electron correlations responsible for this interaction unexpectedly vanish for identical values of the initial and final principal quantum numbers, a fact related to the quasi hydrogenic nature of the high-$l$ Rydberg electron. This special situation, and in particular the vanishing interaction, leads to the surprising observation of an electric \emph{quadrupole} isolated-core excitation with a similar intensity as the neighboring electric dipole transitions.

Terahertz spectroscopy of spin excitations in magnetoelectric LiFePO4 in high magnetic fields

Magnetoelectric multiferroics feature crosscoupling between magnetic and charge order. Here, the authors study the absorption of electromagnetic radiation by spin waves in magnetoelectric LiFePO${}_{4}$ in the terahertz (THz) spectral range. Using linearly polarized THz radiation, they establish that there are spin waves that interact with magnetic $a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d$ electric components of radiation. This is unusual for electron spins since they are susceptible to magnetic fields only. Another striking observation is that the number of spin-wave modes in the THz spectrum exceeds four times the number of modes expected for a four-spin system. Using the mean-field model and the magnetic field dependence of the THz spectra, the authors identify four conventional spin-wave modes in LiFePO${}_{4}$. It is proposed that other THz-active spin-wave modes are more exotic quadrupolar excitations, such as spin-stretching modes and two-magnon excitations.

Observation of giant quadrupole plasmon resonance in C60 in fast ion collisions

Strong perturbation caused due to the Coulomb interaction with fast highly charged ions has been used to probe the quadrupole plasmon excitation in ${\mathrm{C}}_{60}$ fullerene. The electron-emission spectrum arising from a free ${\mathrm{C}}_{60}$ molecule reveals a double-peak structure due to the decay of the giant plasmon resonance. Using a state-of-the-art theoretical approach describing the electron dynamics by time-dependent density functional theory, with an explicit ionic background these two peaks are unambiguously identified as arising from the dipole and quadrupole modes of the plasmon. Furthermore, the electron angular distribution clearly shows a double-well-type distribution which is well reproduced by quadrupole and plasmon resonances. The dipole and quadrupole excitations combined with a long-range postcollisional Coulomb interaction shows excellent agreement with the observed anisotropic angular distribution. The present paper serves as an independent confirmation of the presence of a substantial quadrupole plasmon contribution in molecular systems.

Analog of electromagnetically induced transparency from electric dipole and quadrupole excitation with a Reuleaux triangle split-ring resonator

We simulate, measure, and analyze an electromagnetically induced transparency-like (EIT-like) metamaterial with a unit cell composed of a Reuleaux triangle split-ring resonator (RT-SRR) and a Y-type strip (YS). The transparency peak of the EIT-like metamaterial is located at 12.54 GHz, and the transmission coefficient is 91%. The electric field distributions indicate that the RT-SRR plays the role of the bright mode, and the YS plays the role of the dark mode. The coupling between the bright and dark modes leads to the EIT-like phenomenon. The surface current distributions and the calculated results for the radiated power of the electric multipoles are used to analyze the physical mechanism behind the transparency peak, which can be understood in terms of the electric dipole interacting with the electric quadrupole. As the polarization angle increases, the transmission coefficient of the transparency peak decreases, indicating polarization sensitivity. When the YS is rotated around the center and the RT-SRR is kept fixed, the EIT-like phenomenon appears and disappears. Therefore, the proposed metamaterial has potential applications in detectors and switches. The experimental results are well-matched with the simulation results.

Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet

The microscopic origins of emergent behaviours in condensed matter systems are encoded in their excitations. In ordinary magnetic materials, single spin-flips give rise to collective dipolar magnetic excitations called magnons. Likewise, multiple spin-flips can give rise to multipolar magnetic excitations in magnetic materials with spin S ≥ 1. Unfortunately, since most experimental probes are governed by dipolar selection rules, collective multipolar excitations have generally remained elusive. For instance, only dipolar magnetic excitations have been observed in isotropic S = 1 Haldane spin systems. Here, we unveil a hidden quadrupolar constituent of the spin dynamics in antiferromagnetic S = 1 Haldane chain material Y2BaNiO5 using Ni L3-edge resonant inelastic x-ray scattering. Our results demonstrate that pure quadrupolar magnetic excitations can be probed without direct interactions with dipolar excitations or anisotropic perturbations. Originating from on-site double spin-flip processes, the quadrupolar magnetic excitations in Y2BaNiO5 show a remarkable dual nature of collective dispersion. While one component propagates as non-interacting entities, the other behaves as a bound quadrupolar magnetic wave. This result highlights the rich and largely unexplored physics of higher-order magnetic excitations.

High-performance cross-sandwich Huygens’ metasurface excited by congener quadrupole

Huygens’ metasurface (HMS) can realize high-efficient real-time control of electromagnetic waves through impedance matching,which is specialty of multipoles. Previous designs of HMS mostly focus on realizing 2π phase coverage by combining different poles, while ignoring the limitation on transmittance caused by different attributes between poles. In this paper, we propose a new design of HMS, which can fulfill​ the excitation of the pure magnetic quadrupole (MQ) on target wavelength. Combined with the theory of multipole scattering, we strip off the interference of electric quadrupole by adding glass layers to the cross-shaped units. By optimizing the parameters of the unit after adding glass, we get an HMS element with extremely high transmittance and phase distribution covering full 2π. We found that the peak of MQ will be simultaneously affected by the thickness and position of glass, while the peak position will only be affected by the former. We also characterize the wavefront manipulation performance of the element by designing and simulating typical applications such as beam deflection, focusing and hologram reconstruction. This efficient wavefront modification indicates that multipole analysis is an effective way of dielectric Huygens’ metasurface parameter optimization and can be applied to computer-generated holograms, structured color display devices.