Dipole Hyperfine Interaction Research Articles

The permanent electric dipole moment and hyperfine interactions in platinum monofluoride, PtF

The [11.9]Ω = 3/2 ← X (2)Π(3/2)(0,0) and (1,0) bands of platinum monofluoride, PtF, have been recorded field-free and in the presence of a static electric field. The (19)F(I = 1/2) and (195)Pt(I = 1/2) magnetic hyperfine interactions have been analyzed and compared with predicted values obtained using atomic information and a proposed molecular orbital correlation diagram. The optical Stark shifts were analyzed to produce the permanent electric dipole moments, μ(el), of 2.47(11)D and 3.42(6)D for the [11.9]Ω = 3/2 and X (2)Π(3/2)states, respectively. The observed trend in μ(el) for the PtX (X = C,N,O,S and F) series is discussed and a comparison with IrF made.

Size-dependent magnetic ordering and spin dynamics in DyPO4and GdPO4nanoparticles

Low-temperature magnetic susceptibility and heat-capacity measurements on nanoparticles (d? 2.6 nm) of the antiferromagnetic compounds DyPO4 (TN=3.4 K) and GdPO4 (TN=0.77 K) provide clear demonstrations of finite-size effects, which limit the divergence of the magnetic correlation lengths, thereby suppressing the bulk long-range magnetic ordering transitions. Instead, the incomplete antiferromagnetic order inside the particles leads to the formation of net magnetic moments on the particles. For the nanoparticles of Ising-type DyPO4 superparamagnetic blocking is found in the ac susceptibility at ?1 K, those of the XY-type GdPO4 analog show a dipolar spin-glass transition at ?0.2 K. Monte Carlo simulations for the magnetic heat capacities of both bulk and nanoparticle samples are in agreement with the experimental data. Strong size effects are also apparent in the Dy3+ and Gd3+ spin dynamics, which were studied by zero-field muon spin rotation (?SR) and high-field 31P-nuclear magnetic resonance (31P-NMR) nuclear relaxation measurements. The freezing transitions observed in the ac susceptibility of the nanoparticles also appear as peaks in the temperature dependence of the zero-field ?SR rates, but at slightly higher temperatures, as to be expected from the higher frequency of the muon probe. For both bulk and nanoparticles of GdPO4, the muon and 31P-NMR rates are for T?5 K dominated by exchange-narrowed hyperfine broadening arising from the electron spin-spin interactions inside the particles. The dipolar hyperfine interactions acting on the muons and the 31P are, however, much reduced in the nanoparticles. For the DyPO4 analogs the high-temperature rates appear to be fully determined by electron spin-lattice relaxation processes.

Magneto-optical trapping of bosonic and fermionic neon isotopes and their mixtures: isotope shift of the 3P2 ↔ 3D3 transition and hyperfine constants of the 3D3 state of 21Ne

We have magneto-optically trapped all three stable neon isotopes, including the rare 21Ne, and all two-isotope combinations. The atoms are prepared in the metastable 3P2 state and manipulated via laser interaction on the 3P2 ↔ 3D3 transition at 640.2 nm. These cold (T ≈ 1 mK) and environmentally decoupled atom samples present ideal objects for precision measurements and the investigation of interactions between cold and ultracold metastable atoms. In this work, we present accurate measurements of the isotope shift of the 3P2 ↔ 3D3 transition and the hyperfine interaction constants of the 3D3 state of 21Ne. The determined isotope shifts are (1625.9 ± 0.15) MHz for 20Ne ↔ 22Ne, (855.7 ± 1.0) MHz for 20Ne ↔ 21Ne, and (770.3 ± 1.0) MHz for 21Ne ↔ 22Ne. The obtained magnetic dipole and electric quadrupole hyperfine interaction constants are A(3D3) = (−142.4 ± 0.2) MHz and B(3D3) = (−107.7 ± 1.1) MHz, respectively. All measurements give a reduction of uncertainty by about one order of magnitude over previous measurements.

55Mn nuclear magnetic resonance for antiferromagnetic α-Mn2O3

The zero-field 55Mn nuclear magnetic resonance (NMR) spectra for antiferromagnetic α-Mn2O3 were obtained at low temperatures. The Gaussian-shaped spectrum was positioned around 314 MHz in the zero-temperature limit, and the linewidth was about 5 MHz. The magnetic moment estimated from the resonance frequency was 2.6μB per Mn3+ ion, which corresponds to 65% of 4μB, which is expected when only the contribution of spin to the magnetic moment is considered. The temperature dependence of the sublattice magnetization does not fit Bloch's T2 law well but instead fits the exponential form applicable when there is an initial energy gap in the dispersion relation of the spin wave. From the fitting, we obtained an energy gap of 1.82 meV and an anisotropy energy of 0.22 meV. The spin–spin relaxation time measured as a function of frequency shows that the Suhl–Nakamura interaction is suppressed by this energy gap. The line broadening is mostly influenced by the dipolar hyperfine interaction.

Hyperfine-mediated static polarizabilities of monovalent atoms and ions

We apply relativistic many-body methods to compute static differential polarizabilities for transitions inside the ground-state hyperfine manifolds of monovalent atoms and ions. Knowledge of this transition polarizability is required in a number of high-precision experiments, such as microwave atomic clocks and searches for $\mathit{CP}$-violating permanent electric dipole moments. While the traditional polarizability arises in the second order of interaction with the externally applied electric field, the differential polarizability involves an additional contribution from the hyperfine interaction of atomic electrons with nuclear moments. We derive formulas for the scalar and tensor polarizabilities including contributions from magnetic dipole and electric quadrupole hyperfine interactions. Numerical results are presented for Al, Rb, Cs, ${\mathrm{Yb}}^{+}$, ${\mathrm{Hg}}^{+}$, and Fr.

Hyperfine structure investigation of 187Os atomic levels via optical–optical double resonance

Optical–optical double resonance spectroscopy has been applied to measure the hyperfine structure of spectral line pairs of atomic osmium in the visible wavelength range. In the experiments, enriched isotope samples of either 189Os or 187Os were used. In this way, the magnetic dipole hyperfine interaction constants of the odd isotope 187Os were determined for seven levels of even parity and two levels of odd parity.

A study of the hyperfine structure of Ta I lines based on Fourier transform spectra and laser-induced fluorescence

The hyperfine structure of several spectral lines of the tantalum atom has been investigated by laser excitation in the spectral range 4180–7000 Å. We report the discovery of 14 new energy levels of even parity and 21 new energy levels of odd parity. For the new levels, besides their wave number, their total angular momentum quantum number J, their parity, as well as their magnetic dipole and electric quadrupole hyperfine interaction constants A and B were determined. We classified altogether 73 lines by means of laser spectroscopy in a hollow cathode discharge, 52 of them by laser excitation and 21 via fluorescence decay. Additionally, 120 lines, observed in high-resolution Fourier transform spectra, were classified by using their wave numbers and their characteristic hyperfine patterns.

Comment on the magnetic dipole hyperfine interaction in the gold atom ground state

The multiconfiguration Dirac–Hartree–Fock (MCDHF) model has been employed to calculate the magnetic dipole hyperfine constant A of the 5d106s 2S1/2 ground state of atomic gold. Electron correlation effects contribute more than 20% to the total value of A. We investigated the effects of single, double, and a subset of triple substitutions. The calculations reveal strong cancellations between one-, two- and three-particle correlation effects. It is demonstrated that in the case of the ground state of atomic gold the three-particle effects are comparable in size to the one- and two-particle ones.

Hyperfine Interactions in Graphene and Related Carbon Nanostructures

Hyperfine interactions, magnetic interactions between the spins of electrons and nuclei, in graphene and related carbon nanostructures are studied. By using a combination of accurate first principles calculations on graphene fragments and statistical analysis, I show that both isotropic and dipolar hyperfine interactions in sp2 carbon nanostructures can be accurately described in terms of the local electron spin distribution and atomic structure. A complete set of parameters describing the hyperfine interactions of 13C and other nuclear spins at substitution impurities and edge terminations is determined. These results permit the design of graphene-based nanostructures allowing for longer electron spin coherence times which are required by spintronics and quantum information processing applications. Practical recipes for minimizing hyperfine interactions in carbon nanostructures are given.

Gadolinium (III) ion in liquid water: Structure, dynamics, and magnetic interactions from first principles

We applied first principles molecular dynamics (MD) technique to study structure, dynamics, and magnetic interactions of the Gd(3+) aqua ion dissolved in liquid water, a prototypical system for Gd-based complexes used as contrast agents for magnetic resonance imaging. The first coordination sphere contains eight water molecules with an average Gd-O distance of 2.37 A and an average geometric arrangement close to a square antiprism. The mean tilt angle of the electric dipole vector of these water molecules is theta=145 degrees . In our picosecond time scale simulation we observe no exchange event from the first coordination sphere but only fast "wagging" motions. The second coordination sphere is well pronounced though water molecules in this sphere are subjected to large amplitude dynamic motions. The isotropic hyperfine coupling constants for the inner sphere water molecules [A(iso)((17)O(I))=0.65+/-0.03 MHz, A(iso)((1)H(I))=0.085+/-0.005 MHz] are in good agreement with experimental data and with an earlier study using classical MD. Second sphere Fermi contact hyperfine coupling constants calculated are more than one order of magnitude smaller and of opposite sign as those of the first coordination sphere. The effect of spin polarization induced by the paramagnetic Gd(3+) ion on the dipolar hyperfine interaction was found to be sizable only for the (17)O nuclei of inner sphere water molecules and has a screening character.

Spectral properties of In II from MCDHF calculations

We report extensive relativistic multiconfiguration Dirac–Hartree–Fock calculations of oscillator strengths and hyperfine structures for a large number of electric dipole transitions in In II. Results for the 5s21S0–5s5p3Po0 hyperfine induced transition are also presented. Core polarization is accounted for by means of explicit CI. To describe spin–polarization effects configuration state functions obtained by single excitations from all core-shells are included in the expansions. The computed oscillator strength for the 5s21S0–5s5p3Po1 intercombination transition is in good agreement with laser spectroscopy measurements of In+ ions in a radio-frequency trap. The calculated magnetic dipole hyperfine interaction constants agree very well with experimental constants derived from Fourier transform spectra. The problem with off-diagonal interactions affecting the hyperfine structures in closely spaced fine-structure levels is discussed.

Hyperfine‐Induced f↔f Transitions: Effective Operator Formulation

The direct perturbing influence of the nuclear magnetic and electric multipole hyperfine interactions upon the amplitude of the f↔f electric dipole transitions is analyzed. In this approach, the role of the forcing mechanism is played by an interaction other than the crystal field potential, which is the origin of all existing theoretical models. In particular, new effective operators of the second order that result from the electric dipole hyperfine interactions and compete with the standard Judd–Ofelt terms are introduced. In addition, the tensorial structure of the third‐order effective operators that contribute to the transition amplitude is discussed, and attention is directed to the possibility and necessity of the introduction of a new parameterization scheme of f‐spectra that would be applicable for the description of the hypersensitivity and such transitions that are highly forbidden by the standard selection rules.

Proton NMR study in hexanuclear manganese single-molecule magnets

We report a detailed proton NMR study, as a function of temperature and external magnetic field, of two hexanuclear manganese magnetic molecule clusters with chemical formula $[{\mathrm{Mn}}_{6}{\mathrm{O}}_{2}{({\mathrm{O}}_{2}\mathrm{C}\mathrm{Me})}_{2}{(\text{salox})}_{6}{(\mathrm{Et}\mathrm{O}\mathrm{H})}_{4}]∙4\mathrm{Et}\mathrm{O}\mathrm{H}$ (in short ${\mathrm{Mn}}_{6}$ acetate) and $[{\mathrm{Mn}}_{6}{\mathrm{O}}_{2}{({\mathrm{O}}_{2}\mathrm{C}\mathrm{Ph})}_{2}{(\text{salox})}_{6}{(\mathrm{Et}\mathrm{O}\mathrm{H})}_{4}]∙4\mathrm{Et}\mathrm{O}\mathrm{H}$ (henceforth ${\mathrm{Mn}}_{6}$ benzoate). Both clusters are characterized by a ferrimagnetic ground state with total spin ${S}_{T}=4$ and a large uniaxial anisotropy, which gives rise to an effective energy barrier for the relaxation of the magnetization of the order of ${U}_{\mathrm{eff}}\ensuremath{\sim}28\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The main characteristics of the $^{1}\mathrm{H}$ NMR spectra (measured between $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and room temperature for different fields) are explained in terms of the dipolar hyperfine interaction of the proton nuclei with the adjacent magnetic ions. At low temperatures $(Tl3.5\phantom{\rule{0.3em}{0ex}}\mathrm{K})$, the spectra broaden significantly and become structured due to the slowing down of the local fluctuating fields at the proton sites, caused by the gradual freezing of the ${\mathrm{Mn}}^{3+}$ moments into the ${S}_{T}=4$ collective ground state. The spin dynamics of the exchange coupled magnetic ions was also probed by proton spin-spin relaxation rate ${T}_{2}^{\ensuremath{-}1}$ and spin-lattice relaxation rate ${T}_{1}^{\ensuremath{-}1}$ measurements. On decreasing the temperature, a gradual enhancement of both relaxation rates is observed, followed by a significant decrease of the signal intensity (wipe-out effect). The low frequency regime of the spin fluctuations as probed by ${T}_{1}^{\ensuremath{-}1}$, can be described and analyzed in terms of a single characteristic correlation frequency ${\ensuremath{\omega}}_{c}(T)$, which is interpreted as the lifetime broadening of the discrete magnetic energy levels due to spin-phonon interactions.

Complexation of Copper(II)−Chelidamate: A Multifrequency-Pulsed Electron Paramagnetic Resonance and Electron Nuclear Double Resonance Analysis

Multifrequency electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) techniques were used to obtain structural information about the copper(II)-chelidamate complex. Well-resolved nitrogen ENDOR spectra could be recorded from solid solution samples by using selective excitation of spin packets. Evaluation of nuclear quadrupole and dipolar hyperfine interaction of the directly ligated nitrogen allowed for an identification of the bond direction to the copper ion within the eigen frame of the copper g-matrix. Invoking two-dimensional EPR techniques, additional hyperfine interaction with a "distant" nitrogen spin, identified as resulting from the solvent dimethylformamide (DMF), was observed. The experimental data are only consistent with formation of a stable pseudoplanar copper complex with single solvent ligation via its oxygen atom.

Further experimental investigation of the hyperfine structure in the spectrum of atomic niobium

Laser spectroscopy with either optogalvanic or laser induced fluorescence detection have been employed to measure the hyperfine structure of 25 transitions of atomic niobium in the visible and near infrared spectral range. The magnetic dipole hyperfine interaction constants A of 43 energy levels (22 of even and 21 of odd parity) were determined, 30 of which have been investigated for the first time. The values obtained for the even parity levels are compared with the results of a parametric analysis.

Relativistic theory of the electric quadrupole moment of a hydrogen-like atom in the s 1/2 and p 1/2 states

Relativistic analytical expressions are derived for the electric quadrupole moment induced by the hyperfine interaction of the electron with the nucleus of a hydrogen-like atom in the ns 1/2 and np 1/2 states. The magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The calculations are performed using the generalized virial relationships for the Dirac equation in a central field. The dependences of the electric quadrupole moment on the nuclear charge Z and the principal quantum number n are analyzed. The induced quadrupole moments are compared with the nuclear quadrupole moments.

The permanent electric dipole moment and hyperfine interaction in ruthenium monoflouride (RuF)

Ruthenium monofluoride, RuF, has been detected using low-resolution laser-induced fluorescence (LIF) in the visible and near infrared spectral regions. A visible band, designated as [18.2]5.5-X 4Phi(9/2), has been recorded field-free and in the presence of a static electric field using high-resolution LIF spectroscopy. The r0 internuclear distances for the [18.2]5.5 and X 4Phi(9/2) states were determined to be 1.911 and 1.916 A, respectively. The vibrational interval DeltaG(1/2) of 534(15) cm-1 for the X 4Phi(9/2) state was determined from the analysis of the dispersed LIF. The Stark shifts of the visible band were analyzed to produce permanent electric dipole moments of 1.97(8) and 5.34(7) D for the [18.2]5.5 and X 4Phi(9/2), states, respectively. The fluorine magnetic hyperfine structure associated with spectral features was analyzed. The hyperfine structure and dipole moments are interpreted using a molecular-orbital correlation model and compared with FeF and other ruthenium-containing molecules.

Electric quadrupole moment of a hydrogen-like ion in s and p1/2 states

Relativistic formulas for the electric quadrupole moment of a hydrogen-like atom, induced by the hyperfine interaction, are derived for ns and np1/2 states. Both the magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The formulas are valid for ions with arbitrary nuclear charge and spin. The induced quadrupole moment is compared with the nuclear quadrupole moment for a wide range of hydrogen-like ions.

Spin relaxation of quadrupole nuclei in paramagnetic and magnetically ordered insulators

The longitudinal and transverse spin relaxation through a (generally anisotropic) electron-nucleus interaction in paramagnetic and magnetically ordered insulators is theoretically studied for nuclei with a resolved quadrupole structure. Expressions are derived for the relaxation rates of both the transverse nuclear magnetization components when individual transitions are excited in the quadrupole structure and the total longitudinal nuclear magnetization component. These expressions are reduced to a form that contains the Fourier transforms of the time correlation functions only for the electron spins. Given the specific form of these correlation functions corresponding to different phase states of the electron spins and different origins of their fluctuations, the temperature dependences of the nuclear relaxation rates are ascertained in various cases, including those for dipole and isotropic hyperfine interactions. Calculations are performed for arbitrary electron and half-integer nuclear spins by taking into account the possible quadrupole splitting of the NMR spectrum without any restriction on the smallness of the ratio ℏω s/kBT (ωs is the resonance frequency of the electron spins). The derived expressions are compared with available experimental data on the longitudinal and transverse nuclear relaxation in colossal-magnetoresistance lanthanum manganites in the part of their phase diagram where the corresponding samples are either paramagnetic or magnetically ordered insulators and near the points of transition to an ordered state. Interpretations alternative to the existing ones are offered.

Hyperfine structure in optical spectra of LiYF4-Ho3+: forbidden transitions

The hyperfine lines of the forbidden Γ34 → Γ34 optical transition are observed in the axially polarized absorption spectra of Ho3+ in LiYF4. They are explained by an admixture of nearby lying Γ2 and Γ1 crystal field states by the perpendicular part of the magnetic dipole hyperfine interaction.