Splitting Of Resonance Line Research Articles

Fröhlich resonance splitting in hybrid GaN nanowire-Ag nanoparticle structures

Plasmonic nanoparticles (NPs) have attracted significant attention due to their unique optical properties and broad optoelectronic and photonic applications. We investigate modifications of emission in hybrid structures formed by 60 nm silver NPs and GaN planar nanowires (NWs). Bare GaN NWs exhibit photoluminescence (PL) spectra dominated by broad bands peaking at ∼3.44 eV and ∼3.33 eV, attributed to basal plane stacking faults. In hybrids, two new narrow PL lines appear at 3.36 and 3.31 eV, resulting in PL enhancement at these energies. While the 3.36 eV line in hybrid structures can be explained using the Fröhlich resonance approximation based on the electric dipole concept, the appearance of two features at 3.36 and 3.31 eV indicates the splitting of resonance lines. This phenomenon is explained in framework of theoretical model based on the interaction of the dipole with its charge image, taking into account the quadrupole moment of the silver sphere and the quadrupole field of the charge image. A good agreement is obtained between the calculated Fröhlich resonance frequencies and the experimental PL lines in hybrid structures.

Shifting and Splitting of Resonance Lines due to Dynamical Friction in Plasmas.

A quasilinear plasma transport theory that incorporates Fokker-Planck dynamical friction (drag) and pitch angle scattering is self-consistently derived from first principles for an isolated, marginally unstable mode resonating with an energetic minority species. It is found that drag fundamentally changes the structure of the wave-particle resonance, breaking its symmetry and leading to the shifting and splitting of resonance lines. In contrast, scattering broadens the resonance in a symmetric fashion. Comparison with fully nonlinear simulations shows that the proposed quasilinear system preserves the exact instability saturation amplitude and the corresponding particle redistribution of the fully nonlinear theory. Even in situations in which drag leads to a relatively small resonance shift, it still underpins major changes in the redistribution of resonant particles. This novel influence of drag is equally important in plasmas and gravitational systems. In fusion plasmas, the effects are especially pronounced for fast-ion-driven instabilities in tokamaks with low aspect ratio or negative triangularity, as evidenced by past observations. The same theory directly maps to the resonant dynamics of the rotating galactic bar and massive bodies in its orbit, providing new techniques for analyzing galactic dynamics.

Splitting of resonances in a curved optical fiber-based Fabry-Perot resonator

In this work, the splitting of resonance lines in a Fabry-Perot resonator formed by a section of a standard curved single-mode fiber with metal-coated ends is investigated numerically and experimentally. It is shown that this splitting is similar to the Autler-Townes splitting and results from a strong coupling between the fundamental mode of the core and the whispering gallery mode of the cladding of the curved fiber. The influence of all basic parameters of the curved resonator on the splitting of its resonance lines in the reflection and transmission spectra is considered. Prospects for the practical application of the effects studied for high-resolution optical refractometry, as well as the direction of further research are outlined.

1H and 13C NMR investigation of conformational and aggregation behavior of sodium N-lauroyl sarcosinate

Complementary experiments with NMR 1H and 13C spectroscopy, proton diffusometry, and relaxometry have been used to investigate the sodium N-lauroyl sarcosinate (SLS) micellar systems in aqueous solutions. The effects of concentration and temperature on molecular conformation, micellar structure, and molecular kinetic in the SLS solutions were studied. Each NMR spectral line of the SLS spectrum splits but there are two variants of the effect: (i) for the head-groups this effect exists in the whole concentration range and it is due to the presence of two conformational isomers, (ii) for the hydrophobic part the splitting of resonance lines is observed in certain concentration range and caused by the existence of two different realizations of micellar aggregates. The concentration of the cis-conformers is a bit higher in a “monomer” (diluted) solution as well as the trans-conformers are more favorable in the micellar state. The relation of cis- and trans-conformer fractions is nearly independent of temperature. The transient concentration range, where different types of micellar sub-structures co-exist, is discovered. Moreover, the SLS solutions are characterized by four kinetic processes with different time scale.

Line splitting in the Schumann resonance oscillations

We discuss detection of line splitting in the global electromagnetic (Schumann) resonances. The lifting of resonance degeneracy is usually not visible in the ordinary power spectrum of either the electric or magnetic field components since splitting is small in comparison with the natural width of the resonance lines. Splitting may be detected by exploiting the spatial structure of the fields and/or the elliptical polarization of the magnetic field. The spatial properties were utilized in synchronous and coherent measurements of the vertical electric field at two longitudinally separated observatories. The results were attributed to line splitting. An alternative interpretation was also advanced that takes into account the source‐receiver separation. The lifting of degeneracy also appears as a frequency‐dependent elliptical polarization of the horizontal magnetic field vector, which has been found experimentally. We compare measurement and computational data, and their reciprocity proves the detection of Schumann resonance line splitting.

Recent studies of Schumann resonance and ELF transients

Schumann resonance (SR) is the global electromagnetic phenomenon occurring in the Earth – ionosphere cavity at frequencies of 8, 14, 20 Hz, etc (the ELF band). Phenomenon was named after the author of the pioneer publication on the planetary resonance. Since natural electromagnetic signal originates from lightning strokes distributed worldwide, parameters of oscillations reflect the average condition of ionospheric plasma, spatial distribution and current intensity of thunderstorms. ‘Regular’ lightning strokes occur at a rate of 50 events per second, and their electromagnetic radiation forms the SR background. An irregular or transient component exists caused by relatively rare powerful strokes (the rate is about one event per minute or even less) that provide pulses ten times higher than an ordinary discharge. Three orthogonal field components (vertical electric and two crossed horizontal magnetic fields) are recorded at a Schumann resonance field site, and the power spectra are obtained in the frequency band up to 40 Hz averaged over a few minutes with the typical frequency resolution of 0.1 Hz. The main objective of report is to review the recent results in the Schumann resonance studies. The report consists of two parts; one of them summarizes the experimental data obtained during last 3 – 5 years, while the second describes model studies of ELF radio propagation. We try to mention the most important results in the Schumann resonance. The report surveys the data obtained by using ‘classical’ power spectra acquired at different observatories. Power spectra give information on the properties of the lower ionosphere boundary and on the dynamics of the global thunderstorms. For instance, the sudden changes can be detected in the space weather such as Solar Proton Events (SPE); the regular seasonal motion of thunderstorms is monitored, which is associated with the ground surface temperature; unusual changes might be found in the SR spectra prior to disastrous earthquakes, etc. The cross-spectra of both magnetic fields and magnetic and electric fields (Poynting vector) might be obtained when three field components are recorded. Cross-spectra enhance the coherent fields and reduce the noise thus presenting a more exact information on both the source location and the SR parameters. Elliptical polarization of horizontal magnetic field is measured via the cross-spectra technique, and recent comparison with the model computations proved the detection of Schumann resonance line splitting. Accumulated experimental data present a wide area for resolving the inverse electromagnetic problems directed to establishing an unknown instant distribution of the global lightning activity. Resonance parameters measured worldwide allowed for constructing the effective globally averaged models of the lower ionosphere and the dispersion relation for ELF radio waves. Recent model developments are connected with applications of finite element methods to the resonance problem. Simultaneously, the ‘classical’ spectral field representation was transformed into the time domain providing an effective computational algorithm. Analytical time domain solution allowed generating the quasi–random pulse successions modeling the ELF radio noise. The model time domain ELF signals might be synthesized with predetermined properties. In the conclusion of review, we note a renewal of interest towards the extra-terrestrial Schumann resonance studies. The Huygens probe mission on Titan stimulated interest to distant detection of feasible lightning strokes at the planets and their global location by using the planetary resonance concurrently with studies of ionospheres.

<tex>$Q$</tex>-Factor Measurement of Quasi-Optical Dielectric Resonators Under Conditions of the Whispering Gallery Mode Degeneration Removal

An approach that allows one to determine the unloaded quality factor of a quasi-optical dielectric resonator (QDR) under conditions of the resonance line splitting corresponding to twofold degenerative whispering gallery (WG) mode has been proposed. The resonator is represented by an equivalent network as two oscillatory circuits with a certain coupling between them. The approach allows one to determine the Q-factor of a single oscillatory circuit using three measured parameters, namely: 1) ratio between specific amplitudes of the resonator amplitude-frequency response (or its second derivative); 2) resonant frequency; and 3) frequency splitting of the response (or its respective second derivative). The proposed technique is illustrated by the measurements in the millimeter-wave range for sapphire quasi-optical resonators with conducting and high-T/sub c/ superconducting (HTS) film endplates.

Mapping of strain and electric fields inGaAs/AlxGa1−xAsquantum-well samples by laser-assisted NMR

The usefulness of semiconductor heterostructures derives from the possibility to engineer their electronic and optical properties to match the requirements of many different applications. Optically detected nuclear magnetic resonance provides the possibility to map microscopic properties of such samples with a high spatial resolution through the splitting of resonance lines. In a multiple quantum-well sample, we measure the distortion of the crystal lattice and find variations of the order of ${10}^{\ensuremath{-}5}$ over distances of a few mm. Internal electric fields also cause resonance line splittings. Comparing the electric field-induced resonance line splittings in different quantum wells, we mapped the vertical variation of the electric field from a Schottky contact with a spatial resolution of some 40 nm.

Surface ordering transitions at a liquid crystal-solid interface above the isotropic smectic-A transition.

The degree of orientational order induced by confining cylindrical surfaces is monitored via deuteron nuclear magnetic resonance linesplitting and linewidth above the smectic-A to isotropic phase transition. The orientational order strongly depends on the length of the surfactant coupling molecule, on the surface coverage, and on the liquid crystal. Continuous and stepwise growth of orientational order and surface-induced orientational order transitions found in the isotropic phase are explained in terms of a simplified model of surface-induced layering and molecular self-diffusion.

Cyclotron resonance in the InAs/GaSb heterostructure in an inclined magnetic field

The mechanism of cyclotron resonance line splitting in the InAs/GaSb heterostructure in an inclined magnetic field has been studied experimentally and theoretically. It is shown that the admixing of electron and hole states leads to anticrossing of the Landau levels and, hence, to splitting of the cyclotron resonance line. In the case of an inclined magnetic field, the splitting is not observed, which is explained by the suppression of the admixing of electron and hole states due to the occurrence of an additional barrier for electrons and holes given a longitudinal magnetic field component.

ESR study on α-(BEDT-TTF) 2KHg(SCN) 4 single crystal

X-band ESR measurements have been carried out on a α-(BEDT-TTF) 2KHg(SCN) 4 single crystal at temperatures between 1.5 and 30 K. The principal axis and values of g-tensor are determined. The directions of g 1 = 2.0014, g 2 = 2.0029 and g 3 = 2.0128 are near the directions of the c-, a- and b-axis, respectively. Angular dependence of the effective g-value in the g 1 g 2-plane is much smaller than that in the g 1 g 3- and g 2 g 3-planes. The splitting of resonance line appears below 4.2 K. While the line width of one split line increases with decreasing temperature down to 1.5 K, that of another one is almost independent of temperature. The splitting seems to be related to the SDW state, which is suggested to exist below 8 K.

Membrane-binding peptide from the C2 domain of factor VIII forms an amphipathic structure as determined by NMR spectroscopy.

Factor VIII binds to cell membranes prior to assembling with the serine protease, factor IXa, to form the factor X-activating enzyme complex. In order to better understand the interaction between factor VIII and phosphatidylserine-containing membranes, we have synthesized the membrane-binding peptide from the C2 domain of factor VIII, corresponding to residues 2303-2324. The peptide, fVIII2303-24, with a primary structure of TRYLRIHPQSWVHQIALRMEVL, aggregates at concentrations above 2 microM at pH 7 but is soluble at pH 6. fVIII2303-24 competes with fluorescein-labeled factor VIII (Ki = 3 microM) for binding sites on synthetic phosphatidylserine-containing membranes and for binding sites on stimulated platelets. Circular dichroism spectra indicate that fVIII2303-24 is predominantly a random coil in aqueous solution but adopts a predominantly helical conformation upon interaction with SDS micelles. 1H NMR spectroscopy in the presence of SDS micelles allowed estimation of interproton distances from the nuclear Overhauser effect and estimation of torsion angles from coupling constants indicated by splitting of resonance lines. The distance and angle estimates, processed by distance geometry/simulated annealing software, indicate that fVIII2303-24 has an alpha-helical segment encompassing residues P8-E20 and an extended segment encompassing residues L4-P8. The location of six hydrophobic residues on one face of the structure suggests that hydrophobic interactions contribute to membrane-binding. In addition, two arginines penetrate the hydrophobic plane suggesting that they interact with phosphate moieties in a phospholipid bilayer.

Observation of Mössbauer resonance line splitting caused by Rabi oscillations.

We present the first experimental observation of the Rabi splitting of M\"ossbauer resonance lines. A radio-frequency magnetic field is tuned to induce transitions between hyperfine sublevels of the Zeeman-split excited or ground state of $^{57}\mathrm{Fe}$ nuclei. The line splitting corresponding to the Rabi flopping frequency is observed using a magnetically soft $^{57}\mathrm{FeNi}$ absorber foil of composition with almost zero magnetostriction.

59Co nuclear magnetic resonance study in GdCo2Si2 compound

The spin echo NMR spectra of59Co for GdCo2Si2 are reported. A weak negative hyperfine field on Co nuclei was found in magnetically ordered state of the compound. The splitting of resonance lines in external magnetic field indicates on antiferromagnetic structure of Gd moments lying in thea-a plane with energetic minima in [100] and [110] directions as in GdFe2Si2 and GdNi2Si2.

23Na NMR Study of NaD3(SeO3)2 by the First Order Quadrupole Shift

Temperature dependence of electric field gradient (EFG) at Na site in NaD 3 (SeO 3 ) 2 was studied by the first order shift of quadrupole interaction. The principal coordinate system of EFG at one Na site of the two rotates with varing temperature in the ferroelectric phase. The splitting of resonance lines in the ferroelectric phase shows different behavior against temperature in different direction of the magnetic field. Spontaneous polarization P s was measured on a temperature range from just below the transition to -127°C both along the a and c * axes. Results indicate that P s rotates in the a c plane.

ELF Resonance Line-Splitting in the Earth-Ionosphere Cavity

At extremely low frequencies (ELF), the resonances in the spherical shell between the earth and the ionosphere are excited by natural thunderstorm activity. The frequencies of resonance are determined by the dimensions of the cavity and the conductivities of the earth and the ionosphere. Pronounced resonance ‘mode splitting’ has been observed during periods of high solar activity. After a detailed statistical analysis of ELF data recorded at University of Rhode Island, USA and relevant geo-physical parameters during a major solar event (August, 1972), very significant correlation was found between observation of ‘split’ resonance peaks and maxima of solar proton flux. Results of the statistical analysis have shown that the resonance line splitting is directly related to the enhancement of the solar proton flux and thereby increased ionization in the D-region of the ionosphere.

Resonance modes and the emission recoil-free fraction of a Mössbauer-active impurity atom

The use of time-delayed coincidence technique is proposed to measure the lifetime of nonstationary vibrational resonance states via their influence on the emission recoil-free fraction of an impurity Mössbauer atom. The splitting of resonance lines due to the interactions of impurities is taken into account.

Some Experiments in Nuclear Quadrupole Resonance

Some experiments in nuclear quadrupole resonance suitable for the undergraduate laboratory or senior project are described. The Zeeman splitting of resonance lines and the effect of solid phase transitions may be readily observed with simple apparatus.