Multipole Transitions Research Articles

First spectroscopy of 61Ti and the transition to the Island of Inversion at N = 40

Isomeric states in 59,61Ti have been populated in the projectile fragmentation of a 345 AMeV 238U beam at the Radioactive Isotope Beam Factory. The decay lifetimes and delayed γ-ray transitions were measured with the EURICA array. Besides the known isomeric state in 59Ti, two isomeric states in 61Ti are observed for the first time. Based on the measured lifetimes, transition multipolarities as well as tentative spins and parities are assigned. Large-scale shell model calculations based on the modified LNPS interaction show that both 59Ti and 61Ti belong to the Island of Inversion at N=40 with ground state configurations dominated by particle-hole excitations to the g9/2 and d5/2 orbits.

Study of Relativistic excitation energies and transition data of X–ray and EUV transitions in Be-like ions

In the present work, fine structure energies, transition wavelengths, transition rates, oscillator strengths and line strengths have been presented for lowest 40 levels of Be-like Fe, Os to Hg ions by using GRASP2K. We have analyzed the effects of core-valence (CV) correlations in excitation energies as a function of active set. We accomplish that effects of core-valence correlations are necessary to attain accuracy and convergence in excitation energies. We have compared our presented excitation energies of Be-like Fe with available theoretical and experimental energies and found good agreement. But due to unavailability of data for Be-like Os to Hg ions for comparison, we have calculated excitation energies from flexible atomic code (FAC). We show that magnetic multipole transitions (M2) have effective contribution in lifetime of 2s3p 3P2o and 2p3d 3P2o. We demonstrate that transitions of Be-like ions among lowest 40 levels mainly occurs in Hard X-ray (HXR), Soft X-ray(SXR) and Extreme Ultraviolet (EUV) regions.

Ambit: A programme for high-precision relativistic atomic structure calculations

We present the ambit software package for general atomic structure calculations. This software implements particle–hole configuration interaction with many-body perturbation theory (CI+MBPT) for fully relativistic calculations of atomic energy levels, electric- and magnetic-multipole transition matrix elements, g-factors and isotope shifts. New numerical methods and modern high-performance computing techniques employed by this software allow for the calculation of open-shell systems with many valence-electrons (N≥5) to a high degree of accuracy and in a highly computationally efficient manner. Program summaryProgram Title:ambitProgram Files doi:http://dx.doi.org/10.17632/7xfxhr9mg6.1Licensing provisions: GPLv3Programming language: C++11Nature of problem: Calculation of atomic/ionic spectra, including energy levels, electric and magnetic multipole transition matrix elements, and isotope shifts.Solution method: The programme calculates energy levels and wavefunctions using either configuration interaction (CI) only, or CI with many-body perturbation theory (CI+MBPT) in the Brillouin–Wigner MBPT formalism.Restrictions: The programme is not designed to treat highly-excited (Rydberg) states or continuum processes to a high degree of accuracy.Additional comments: Programme github repository

First-principles modeling of x-ray Raman scattering spectra

X-ray Raman scattering (XRS) spectroscopy is a rapidly developing synchrotron-based technique employed to probe the local electronic structure of condensed matter. The use of hard x-rays makes XRS particularly well-suited for studying low-energy edges of bulk materials, even under highly absorbing sample environments, opening up a wealth of possibilities for $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ experiments. Here, the authors propose an efficient method for calculating $K$-edge XRS spectra, developed within the framework of density functional theory and designed to fully account for the electric multipole transitions observed when a finite momentum is transferred to the photoelectron.

Precise measurement of αK and αT for the 39.8-keV E3 transition in Rh103 : Test of internal-conversion theory

Neutron-activated sources of $^{103}$Ru and $^{103}$Pd both share the isomeric first-excited state in $^{103}$Rh as a daughter product. From independent measurements of both decays, we have measured the $K$-shell and total internal conversion coefficients, $\alpha_K$ and $\alpha_T$, for the 39.8-keV $E$3 transition, which de-excites that state in $^{103}$Rh, to be 141.1(23) and 1428(13), respectively. When compared with Dirac-Fock calculations, our new results disagree with the version of the theory that ignores the $K$-shell atomic vacancy, which is consistent with our conclusion drawn from a series of measurements on high multipolarity transitions in nuclei with higher $Z$. Calculations that include the atomic vacancy indicate that the transition actually has a small $M$4 component with mixing ratio $\delta$ = 0.023(5).

Resonance Energy Transfer in Arbitrary Media: Beyond the Point Dipole Approximation

In this work, we present a comprehensive theoretical and computational study of donor/acceptor resonance energy transfer (RET) beyond the dipole approximation, in arbitrary inhomogeneous and dispersive media. The theoretical method extends Forster theory for RET between particles (molecules or nanoparticles) to the case where higher multipole transitions in the donor and/or acceptor play a significant role in the energy transfer process. In our new formulation, the energy transfer matrix element is determined by a fully quantum electrodynamic expression, but its evaluation requires only classical electrodynamics calculations. By means of a time domain electrodynamical approach (TED), the matrix element evaluation involves the electric and magnetic fields generated by the donor and evaluated at the position of the acceptor, including fields associated with transition electric dipoles, electric quadrupoles, and magnetic dipoles in the donor, and the acceptor response to the electric and magnetic fields and ...

Theoretical study of energy levels and radiative properties of Be-like W70+

We report an extensive theoretical study of the Be-like W70+ spectrum in a wide energy range. We present accurate calculated 215 fine-structure energy levels related to the configurations 1s22s2, 1s22p2, 1s2nƖn′l′ (n = 2, n′ = 2–7 Ɩ = s, p Ɩ′ = s, p, d, f, g), which may be useful ion for fusion plasma research. We have identified wavelengths of extreme ultraviolet (EUV) and X-ray transitions using the multiconfiguration Dirac-Hartree-Fock (MCDHF) method implemented in the GRASP2K code. The calculations are carried out in the active space approximation with the inclusion of the Breit interaction, the finite nuclear size effect, and quantum electrodynamic corrections. Transition data are reported for multipole transitions from the ground state. We have discussed discrepancy graphically with available results. We have also graphically explained the convergence in excitation energies with active sets. We predict new energy levels and transition parameters where no other experimental or theoretical results are available. The present complete set of results should be of help in line identification and the interpretation of spectra, as well as in modeling and diagnostics of fusion plasmas.

Large-scale Multiconfiguration Dirac–Hartree–Fock and Relativistic Configuration Interaction Calculations of Transition Data for B-like S xii

Abstract Excitation energies and lifetimes for the 213 lowest states of the n ≤ 5 configurations in B-like S xii are calculated using highly correlated wave functions, optimized with the fully relativistic multiconfiguration Dirac–Hartree–Fock method. Multipole transition rates and associated radiative data (line strengths and oscillator strengths) for transitions connecting these levels are also reported. The theoretical excitation energies are systematically compared with the NIST Atomic Spectra Database in which misidentifications are pointed out. After eliminating the latter, a mean energy difference with the standard deviation between computed and observed energies of 12 ± 341 cm−1 is obtained for the n ≥ 3 high-lying states. This level of accuracy confirms that elaborate ab initio calculations can assist in the identification of new emission lines in the solar and other astrophysical spectra. The present work provides atomic data of high accuracy for an ion of astrophysical interest, B-like S xii, for which experimental data are scarce.

Electric quadrupole channel of the 7.8 eV Th229 transition

The unique isomeric transition at 7.8 eV in $~^{229}\mathrm{Th}$ has a magnetic dipole ($M1$) and an electric quadrupole ($E2$) multipole mixing. So far, the $E2$ component has been widely disregarded. Here, we investigate the nuclear physics nature and the impact of the $E2$ decay channel for the nuclear coupling to the atomic shell based on the newest theoretical predictions for the corresponding reduced nuclear transition probabilities. Our results show that the contribution of the $E2$ channel is dominant or at least of the same order of magnitude for internal conversion or electronic bridge transitions involving the atomic orbitals $7p$, $6d$ and $5f$. Notable exceptions are the internal conversion of the $7s$ electron and the electronic bridge between the electronic states $7s$ and $7p$, for which the $M1$ component dominates by two to three orders of magnitude. Caution is therefore advised when considering isomeric excitation or decay via nuclear coupling to the atomic shell, as the involved orbitals determine which multipole transition component dominates.

Selection rules for electric multipole transition of triatomic molecule in scattering experiments**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300), the National Natural Science Foundation of China (Grant No. U1732133), and the Science Fund from Chinese Academy of Sciences (Grant No. 11320101003).

In the electron or x-ray scattering experiment, the measured spectra at larger momentum transfer are dominated by the electric dipole-forbidden transitions, while the corresponding selection rules for triatomic molecules have not been clearly elucidated. In this work, based on the molecular point group, the selection rules for the electric multipolarities of the electronic transitions of triatomic molecules are derived and summarized into several tables with the variation of molecular geometry in the transition process being considered. Based on the summarized selection rules, the electron energy loss spectra of H2O, CO2, and N2O are identified, and the momentum transfer dependence behaviors of their valence-shell excitations are explained.

Energy Levels, Lifetimes, and Transition Rates for P-like Ions from Cr x to Zn xvi from Large-scale Relativistic Multiconfiguration Calculations

Abstract The fully relativistic multiconfiguration Dirac–Hartree–Fock method is used to compute excitation energies and lifetimes for the 143 lowest states of the , 3s3p 4, , 3s3p 33d, 3p 5, configurations in P-like ions from Cr x to Zn xvi. Multipole (E1, M1, E2, M2) transition rates, line strengths, oscillator strengths, and branching fractions among these states are also given. Valence–valence and core–valence electron correlation effects are systematically accounted for using large basis function expansions. Computed excitation energies are compared with the NIST ASD and CHIANTI compiled values and previous calculations. The mean average absolute difference, removing obvious outliers, between computed and observed energies for the 41 lowest identified levels in Fe xii, is only 0.057%, implying that the computed energies are accurate enough to aid identification of new emission lines from the Sun and other astrophysical sources. The amount of energy and transition data of high accuracy are significantly increased for several P-like ions of astrophysics interest, where experimental data are still very scarce.

4f Crystal Field Ground State of the Strongly Correlated Topological Insulator SmB_{6}.

We investigated the crystal-electric field ground state of the 4f manifold in the strongly correlated topological insulator SmB_{6} using core-level nonresonant inelastic x-ray scattering. The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the Γ_{8} quartet state of the Sm f^{5} J=5/2 configuration governs the ground-state symmetry and, hence, the topological properties of SmB_{6}. Our findings contradict the results of density functional calculations reported so far.

Scattering of anti-plane shear waves by arbitrarily distributed circular cylinders in a functionally graded multiferroic fibrous composite

In this work, a theoretical framework is developed for the multiple scattering of an anti-plane shear wave by a functionally graded multiferroic fibrous composite. The composite consists of arbitrarily distributed circular cylinders and may have different sizes and material constituents. The cylinders are exponentially graded along the radial direction. We exploit the multipole expansions, transition matrix, and Graf’s addition/binomial expansion theorems to obtain a complete solution of the multiple scattering problem in the scenario of functionally graded multiferroic composites. These solved magneto-electro-elastic fields are then used to obtain the directivity patterns of the scattered wave, dynamic stress (electric displacement/magnetic flux) concentration factors, and scattering cross sections. Numerical results reveal the profound influence of the functionally graded parameter, the material properties of constituent phases, the number of inclusions, as well as the frequency of a propagating SH wave on the scattered field induced by the functionally graded fibers. It is expected that the formulation and numerical results serve as useful references for the design and manufacture of functionally graded piezoelectric–piezomagnetic fibrous composites under dynamic loadings.

Partial-wave analysis and multipole transition interferences in the breakup of 6Li on 152Sm target

We have performed a detailed partial-wave analysis in order to analyze each partial-wave contribution to the breakup cross-sections as well as multipole interference effects in the [Formula: see text] breakup reaction. The results show that [Formula: see text]-waves contribute up to 67.03% of the overall integrated total breakup cross-section, distributed as follows: 10.43% for the [Formula: see text] partial-wave, 21.94% for the [Formula: see text] partial-wave and 34.66% for the [Formula: see text] partial-wave. A similar trend is observed for both Coulomb and nuclear breakup cross-sections. The importance of [Formula: see text]-waves over the non-[Formula: see text]-waves in the breakup process is mainly due to the higher-order multipole interferences. It is also obtained that the combination of [Formula: see text]-waves and [Formula: see text]-waves accounts for 84.77%, 89.95% and 73.58% of the total, Coulomb and nuclear breakup cross-sections, respectively. Considering the results obtained for the [Formula: see text] and [Formula: see text] partial-waves, we conclude that the [Formula: see text] and [Formula: see text] resonant breakup cross-sections, which can be obtained by integrating over the resonant energy range, could not be negligible compare to the [Formula: see text] resonant breakup cross-section. As far as this reaction is concerned, we can conclude that in the sequential breakup of [Formula: see text], excitations to all its three resonant states should be considered for a fair description of such process.

Circular dichroism of twisted photons in non-chiral atomic matter

We calculate the circular dichroism (CD) for the absorption of the twisted photons, or optical vortices, by atoms, caused by atomic excitation into discrete energy levels. The effects of photon spin on the rates and cross sections of atomic photo-excitation are considered. It is demonstrated that, although for electric dipole transitions the atomic excitation rates depend on the relative orientation of photon spin and orbital angular momentum (OAM), the resulting CD is zero. However, CD is nonzero for atomic transitions of higher multipolarity, and it is predicted to peak near the phase singularity in the optical vortex center. The effects remain large in a paraxial limit, where analytic expressions are provided. The predicted spin asymmetries are equivalent to OAM dichroism for the fixed photon spin.

Multipolar Graviton in the Hydrogen Atoms

We derive multipolar gravitational radiation in the framework of quantum field theory in which the atomic states are treated nonrelativistically, and the gravitational waves are quantized. By relaxing the constraint eik·x ≈ 1, the multipolar transition rate is calculated when one graviton is emitted. As a consistency check, we recover the semiclassical result in the dipole approximation regime. Besides, we show that the dynamical mechanism that gives rise to spontaneous graviton emission by an atom, has a profound consequence on the lifetime of the atomic electron.

Molecular-frame EELS experiment on inner-valence ionization of N2

SynopsisWe report molecular-frame electron scattering cross sections of N2, obtained using an electron-ion coincidence technique. The vector correlation between the scattered electron and the fragment ion has been measured at incident electron energy of 1.4 keV for inner-valence ionization of N2. The angular distributions of the electron scattering cross sections thus obtained exhibit clear momentum transfer dependence, indicating the significant change of the ionization dynamics due to contributions from electric multipole transitions.

High-order multipole radiation from quantum Hall states in Dirac materials

We investigate the optical response of strongly disordered quantum Hall states in two-dimensional Dirac materials and find qualitatively different effects in the radiation properties of the bulk versus the edge. We show that the far-field radiation from the edge is characterized by large multipole moments (> 50) due to the efficient transfer of angular momentum from the electrons into the scattered light. The maximum multipole transition moment is a direct measure of the coherence length of the edge states. Accessing these multipole transitions would provide new tools for optical spectroscopy and control of quantum Hall edge states. On the other hand, the far-field radiation from the bulk appears as random dipole emission with spectral properties that vary with the local disorder potential. We determine the conditions under which this bulk radiation can be used to image the disorder landscape. Such optical measurements can probe sub-micron length scales over large areas and provide complementary information to scanning probe techniques. Spatially resolving this bulk radiation would serve as a novel probe of the percolation transition near half-filling.

New systematic features in the neutron-deficient Au isotopes

A recently developed portable, on-line capability for γ-ray and conversion-electron spectroscopy, HIGH-TATRA is demonstrated with its application to the study of 183Hg 183Au at ISOLDE. Key details of the low-energy level scheme of the neutron-deficient nuclide 183Au populated in this decay are presented. A broad energy germanium detector is employed to achieve this (the first-ever use of such a device in decay-scheme spectroscopy), by way of a combination of high-gain γ-ray singles spectroscopy and γ–γ coincidence spectroscopy. Further, by combining the γ-ray detectors with a liquid-nitrogen-cooled Si(Li) detector operated under high vacuum, conversion-electron singles and e–γ coincidences are obtained. These data lead to the determination of transition multipolarities and the location of a highly converted (E0 + M1 + E2) transition in the 183Au decay scheme, suggesting a possible new shape coexisting structure in this nucleus. Identification of new intruder and normal states fixes their relative energies in 183Au for the first time. New systematic features in the odd-Au isotopes are presented.

Precise measurement of αK and αT for the 109.3-keV M4 transition in Te125 : Test of internal-conversion theory

We have measured the K-shell and total internal conversion coefficients (ICCs), alpha_K and alpha_T, for the 109.3-keV M4 transition in 125Te to be 185.0(40) and 350.0(38), respectively. Previously this transition's ICCs were considered anomalous, with alpha values lying below calculated values. When compared with Dirac-Fock calculations, our new results show good agreement. The alpha_K result agrees well with the version of the theory that takes account of the K-shell atomic vacancy and disagrees with the one that does not. This is consistent with our conclusion drawn from a series of high multipolarity transitions.