Linewidth Parameters Research Articles

Distortion of the p-mode peak profiles by the solar-cycle frequency shifts: do we need to worry?

We seek to address whether solar-cycle frequency shifts of the Sun's low-l p modes ‘distort’ the underlying shapes of the mode peaks, when those peaks are observed in power frequency spectra made from data spanning large fractions, or more, of the cycle period. We present analytical descriptions of the expected profiles, and validate the predictions through use of artificial seismic time-series data, in which temporal variations of the oscillator frequencies are introduced. Our main finding is that for the Sun-like frequency shifts the distortion of the asymmetrical Lorentzian-like profiles is very small, but also just detectible. Our analysis indicates that by fitting modes to the usual Lorentzian-like models – which do not allow for the distortion – rather than new models we derive, there is a bias in the mode height and linewidth parameters that is comparable in size to the observational uncertainties given by multi-year data sets. Bias in the frequency parameter gives much less cause for worry, being over an order of magnitude smaller than the corresponding frequency uncertainties. The distortion discussed in this paper may need to be considered when multiyear Sun-like asteroseismic data sets are analysed on stars showing strong activity cycles.

Electron paramagnetic resonance (EPR) and stable isotope records of paleoenvironmental conditions during peat formation

EPR spectroscopy was performed on four peat cores (1–2.5 m depth) collected from Yellowstone National Park (USA), Scotland (UK) and Lower Silesia (Poland) to study peat formation process. The stable free radicals identified in all investigated samples are semiquinone type and g-parameters range from 2.0030 to 2.0048. The highest g-values are characteristic of upper well-aerated peat layers and gradually decrease with depth. The lowest g-values are typical of relatively old fens and bogs where anaerobic conditions are expected and carbonization processes are advanced. The decrease in g-parameter value is connected with conjugation of semiquinone units with gradually augmented polyaromatic units in the peat substance. Generally the radical concentration increases with depth (0.05–5 × 10 17 spins/gram). However the g-values, line width parameters, and spin concentrations exhibit strong variations in some peat layers. Variation of these parameters observed for certain peat horizons correlate with the variation of carbon stable isotopic composition. For the old well-conserved peat deposits (e.g. Scotland/UK, ∼5600BP), variation of EPR parameters may be used to study paleo redox conditions.

EPR studies on single crystals of [formula omitted

Electron paramagnetic resonance (EPR) studies are carried out on single crystals of Pr 1 - x Pb x MnO 3 , for x = 0.23 and 0.30. The crystal with x = 0.23 undergoes a transition from paramagnetic insulator to ferromagnetic insulator with Curie temperature T C ∼ 167 K . The crystal with x = 0.30 undergoes a transition from paramagnetic insulator to ferromagnetic metal with T C ∼ 200 K . The EPR analysis is carried out in the paramagnetic region for both the crystals. The EPR signals are fitted to the Dysonian equation. Linewidth, intensity and asymmetry parameters are plotted as a function of temperature down to T C . The intensity shows a simple Curie–Weiss behaviour. The spin relaxation takes place through a “bottleneck” mechanism according to which linewidth depends only on strong exchange interaction between Mn 3 + and Mn 4 + ions. Around 240 K a secondary low field EPR signal is observed for both compositions which persists till around 200 K indicating a possible phase separation.

Simulation of mask proximity printing

The paper presents a simulation approach for mask proximity printing. The simulation steps include image formation in air and in photoresist, post-exposure bake, and chemical development and analysis of resist profiles. The intensity distribution in air and in resist in proximity distance from the mask is described by a fast frequency domain method that is based on scalar diffraction analysis. The accuracy and the performance of the method are compared with rigorous electromagnetic field computations that take mask topography effects and the finite conductivity of absorber materials into account. The computed intensity distributions inside the resist are coupled to an established standard simulation flow, which is also used in the simulation of projection printing. The resulting resist profiles can be evaluated in terms of linewidth, sidewalls, and other parameters. Finally, an application of the simulation procedure for the simulation of process windows and optimization of linewidth biasing is shown.

Radiation-pressure-induced mode splitting in a spherical microcavity with an elastic shell

In this work, we present a novel method to reveal azimuthal whispering gallery modes (WGMs) in a spherical microcavity coated with a nano-meter thick polyelectrolyte shell and one monolayer of CdTe semiconductor quantum dots. The new approach in this experiment is based on the deformation of the spherical shape in a non-contact way using the radiation pressure from a laser beam, which causes the lifting of the degeneracy of the WGMs. The resonance peak linewidth and splitting parameters can be efficiently controlled by the strength of the radiation pressure and the elastic properties of the surface shell.

Circular dichroism spectrum of [Co(en)3]3+ in water: A discrete solvent reaction field study

AbstractIn this work we investigate the circular dichroism (CD) spectrum of [Co(en)3]3+ in water, using the discrete solvent reaction field (DRF) model. The DRF model is a polarizable quantum mechanics/molecular mechanics (QM/MM) model. The implementation of the DRF model for CD spectra calculations based on time‐dependent density functional theory (TDDFT) is presented. The combination of DRF with TDDFT allows for a computationally attractive solution for calculating chirooptical properties of molecules in solution when explicit solvent structures are of interest. Using a mixed coarse/fine‐grained parallel computation, we show that average CD spectra from snapshots of the solvent structure can be obtained routinely. Classical polarizable molecular dynamics (MD) simulations have been used to obtain the solvent structure around the [Co(en)3]3+ (en = ethyldiamine) solute. We show that the final spectrum converges quickly with respect to the number of configurations. The DRF results were compared with results obtained from the much simpler conductor‐like screening model (COSMO). Both models predicted similar blue shifts of the CD bands, but none of the models is in perfect agreement with the experiments. For instance, the calculated intensities are larger than what is found experimentally if reasonable empirical line width parameters are applied. From the DRF computations, we further show that almost all the solvent effects arise from ground‐state solvation. Thus, ignoring the dynamic solvent response is a good approximation for a system like [Co(en)3]3+, where the solute is highly charged and the solvent is very polar. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006

EPR studies on Cu 2+ and Co 2+ complexes of tetraaza porphyrin derivatives

The electron paramagnetic resonance (EPR) investigations on 2,9,17,23-tetra-((1,1,2-(tricarbethoxyethyl)) phthalocyanine, 2,9,16,23-tetra-(carboxymethyl)-3,10,17,24-tetrachloro-phthalocyaninato complexes and octakis-(1-naphthyl-methylthio) substituted porphyrazine derivatives coordinated by Co 2+ and Cu 2+ ions have been performed in the temperature range of 10–300 K. The EPR spectra indicate axially symmetric character of ligand field at site of the Co 2+ and Cu 2+ paramagnetic ions consistent with the planar structure of each complex. Especially, the Cu 2+ coordinated compounds show important covalency effects with neighbouring N atoms with decreasing temperature, whereas absorption intensities obey the Curie law for both type paramagnetic ion coordinated complexes. The computer programs have been written to determine Spin-Hamiltonian and EPR linewidth parameters for both solid powder and solution forms of ion coordinated complexes. Orbital energy levels for magnetic electrons were determined from Spin-Hamiltonian parameters as well.

Conformational Studies of the Tetramerization Site of Human Erythroid Spectrin by Cysteine-Scanning Spin-Labeling EPR Methods

We used cysteine-scanning and spin-labeling methods to prepare singly spin labeled recombinant peptides for electron paramagnetic resonance studies of the partial domain regions at the tetramerization site (N-terminal end of alpha and C-terminal end of beta) of erythroid spectrin. The values of the inverse line width parameter (deltaH0(-1)) from a family of Sp alphaI-1-368delta peptides scanning residues 21-30 exhibited a periodicity of approximately 3.5-4. We used molecular dynamics calculations to show that the asymmetric mobility of this helix is not necessarily due to tertiary contacts, but is likely due to intrinsic properties of helix C', a helix with a heptad pattern sequence. The residues with low deltaH0(-1) values (residues at positions 21, 25, and 28/29) were those on the hydrophobic side of this amphipathic helix. Native gel electrophoresis results showed that these residues were functionally important and are involved in the tetramerization process. Thus, EPR results readily identified functionally important residues in the alpha spectrin partial domain region. Mutations at these positions may lead to clinical symptoms. Similarly, the deltaH0(-1) values from a family of spin-labeled Sp betaI-1898-2083delta peptides also exhibited a periodicity of approximately 3.5-4, indicating a helical conformation in the two scanned regions (residues 2008-2018 and residues 2060-2070). However, the region consisting of residues 2071-2076 was in a disordered conformation. Both helical regions include a hydrophilic side with high deltaH0(-1) values and a hydrophobic side with low deltaH0(-1) values, demonstrating the amphipathic nature of the helical regions. Residues 2008, 2011, 2014, and 2018 in the first scanned region and residues 2061, 2065, and 2068 in the second scanned region were on the hydrophobic side. These residues were critical in alphabeta spectrin association at the tetramerization site. Mutations at some of these positions have been reported to be detrimental in clinical studies.

Temperature Broadening of LH2 Absorption in Glycerol Solution

In order to determine the relationship between the pigment-protein and the pigment-pigment interactions, the measurements of absorption spectra of the peripheral light-harvesting complex LH2 from the purple bacteria Rhodobacter sphaeroides solvated in glycerol/buffer solution were carried out in a wide temperature range, from 4 to 250 K. The SDFs used for simulating the temperature dependence of B800 and B850 bands were determined in a parametric form. To fit experimental spectra the overall exciton-phonon coupling had to be assumed to be weak for B850 (lambda/2V approximately 0.3, where lambda is the reorganization energy and V is the nearest-neighbor dipole-dipole coupling for bacteriochlorophylls). At physiological temperatures the intermediate nuclear bath dynamics compares with the magnitude of energy gap fluctuations. Slower dynamics with kappa approximately 0.39, where kappa is the ratio of the nuclear relaxation rate and the line width parameter, determines the spectral shape of B850 whilst faster modulations characterize B800 (kappa approximately 2.39). The static disorder for the B800 band is relatively high with the characteristic value of the inhomogeneous bandwidth Gamma(inh) approximately 120 cm-1, while for the B850 band this value is almost equal to the dipole-dipole coupling strength (Gamma(inh) approximately 360 cm-1). It has been found that the LH2 absorption spectrum is likely to be influenced by the temperature dependence of the dielectric constant of the solution in the high temperature range, when the glycerol/buffer solution is in the liquid state.

Pressure broadening and fine-structure-dependent predissociation in oxygen BΣu−3, v=

Both laser-induced fluorescence and cavity ring-down spectral observations were made in the Schumann-Runge band system of oxygen, using a novel-type ultranarrow deep-UV pulsed laser source. From measurements on the very weak (0,0) band pressure broadening, pressure shift, and predissociation line-broadening parameters were determined for the B 3sigma(u)-, v = 0,F(i) fine-structure components for various rotational levels in O2. The information content from these studies was combined with that of entirely independent measurements probing the much stronger (0,10), (0,19), and (0,20) Schumann-Runge bands involving preparation of vibrationally excited O2 molecules via photolysis of ozone. The investigations result in a consistent set of predissociation widths for the B 3sigma(u)-, v = 0 state of oxygen.

Hyperfine structure and interstellar curves of growth

The effects of the hyperfine structure (HFS) that is present in some interstellar absorption lines are investigated in the case of a single absorbing cloud. If the respective total equivalent widths of two or more unresolved HFS multiplets measured in relatively low-resolution spectra are analysed specifically by means of a curve of growth, the column density N(X) and the linewidth parameter b(X) inferred for absorbing species X in the cloud will generally be in error if the HFS is ignored. The fundamental physical effect is the reduced line saturation that arises because the total column density is divided among the HFS levels of the ground atomic level, each of which generally gives rise to an HFS line at a different wavelength. For nuclear spins / = 3/2 and / = 5/2, theoretical curves of growth are calculated for some of the resonance lines of some alkali atoms, for each of four illustrative choices of the parameter α = A/b, the ratio of the HFS splitting in the ground atomic level to the linewidth. Applications of the results to interstellar absorption by NaI, KI and Al III are emphasized. HFS is, fortunately, unimportant for most interstellar lines, however. Among the 35 elements that have been detected in diffuse clouds via interstellar absorption in the ultraviolet/optical spectral region, the most abundant isotope of each of 25 of these shows no HFS, because I = 0 or, in the relevant ground atomic level, J = 0.

Optimization of the Phase-Locked Flux-Flow Oscillator for the submm Integrated Receiver

The Superconducting Integrated Receiver (SIR) comprises in one chip a planar antenna integrated with an SIS mixer, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and a second SIS harmonic mixer (HM) for FFO phase locking. Free-running FFO linewidth well below 10 MHz is required to ensure phase-locked operation of an SIR. Comprehensive experimental study of the Nb-AlOx-Nb FFO linewidth and other main parameters has been carried out in order to achieve this goal. Essential dependence of the FFO linewidth on its width and idle region dimension has been found. It makes possible an optimization of the FFO design and selection of the best FFO parameters for practical operation of the SIR.

Intercomparison between ozone-broadening parameters retrieved from millimetre-wave measurements by using different techniques

For atmospheric purposes, the N 2- and O 2-, or Air-broadenings of selected transitions of ozone have been investigated in the 195–300 K temperature range. More precisely, the following 13 transitions in the 280–345 GHz frequency range have been studied: the 2 2,0 ← 2 1,1 (279.5 GHz), 24 2,22 ← 24 1,23 (286.2 GHz), 3 2,2 ← 3 1,3 (286.3 GHz), 5 2,4 ← 5 1,5 (293.2 GHz), 13 4,10 ← 14 3,11 (300.7 GHz), 14 0,14 ← 13 1,13 (301.8 GHz), 7 2,6 ← 7 1,7 (303.2 GHz), 26 2,24 ← 26 1,25 (315.9 GHz), 5 3,3 ← 6 2,4 (317.2 GHz), 20 1,19 ← 20 0,20 (320.0 GHz), 26 6,20 ← 27 5,23 (343.2 GHz), 26 2,24 ← 25 3,23 (343.2 GHz), and 4 3,1 ← 5 2,4 (343.5 GHz) lines. Systematic errors are known to be the principal error source and recent intercomparisons of line-broadening coefficients showed differences up to 20%, thus a large effort in minimizing systematic error sources has been taken and cross check measurements with different techniques have been carried out. The conclusion of the intercomparison performed indicates an excellent agreement of the results and that an uncertainty less than 3%, which also takes into account the systematic errors, can be claimed for the line-broadening parameters.

Collisional parameters of [formula omitted] lines: effect of temperature

High-resolution Fourier transform spectra of H 2 O –air mixtures have been measured at 296, 742, and 980 K for total pressures of 0.5 and 1.0 atm in the region of the ν 2 band. From these recordings, air-broadening coefficients have been determined for the doublet lines with K c = J . From these data and previous experimental determinations, line-broadening parameters γ ( T ) are obtained at all three temperatures for the doublet lines from J = 0 up to 16. These values are then used to deduce the temperature-dependence exponent n such that γ ( T ) = γ ( 296 ) × ( 296 / T ) n . The values of n obtained using the two elevated temperatures are consistent and show that line widths decrease with T for small J-values ( n ≈ + 0.8 ) , are almost temperature independent on T for J ≈ 10 , and increase with T for high J lines ( n ≈ - 0.3 for J ≈ 15 ). This original result, which confirms theoretical predictions made about 15 years ago with a semi-classical approach (J. Chem. Phys. 86 (1987) 144), is analyzed here using an improved version of the model. Comparisons between measured and computed widths show that calculations cannot correctly reproduce the experimental results at all temperatures simultaneously. This failure is attributed to the use of an inappropriate interaction potential and to the very strong dependence of the broadening γ ( v ) on the relative velocity v for high J lines. This strong variation of γ ( v ) raises the question (which is discussed here) of what calculated quantity is to be compared with measured values (i.e. γ [ v ¯ ( T ) ] , [ γ ( v ) ] ¯ ( T ) , or some other more complex mean to account for the velocity averaging of the spectral profile itself?). Nevertheless, when the temperature exponent n is considered, satisfactory agreement between experiments and predictions is obtained, particularly when the averaging of widths over the relative velocity distribution is made.

EPR studies on the dynamics of the structure of copper (II) doped silica gels

Detailed X-band EPR studies on 1.0 mol% copper oxide doped silica gels, oven dried as well as calcined at various temperatures up to 1000 °C have been carried out in the temperature range 10.4–300 K. Spin Hamiltonian and line-width parameters are determined by computer simulation of the observed spectra. Important information derived on the dynamics of the porous structure of Cu-doped silica gel in the light of the EPR parameters is as follows: (i) Three kinds of Cu 2+ species (including one Cu-pair) are present in the 100 °C oven dried silica gel. (ii) Two kinds of slow rotating isolated Cu 2+ species (one Cu 2+ pair) occur in the 400 °C calcined sample at room temperature. The Cu-pair species agglomerate at low temperatures (⩽200 K) to form CuO clusters which remain undetected apparently because of their large line-width. (iii) Only one kind of Cu-species is detected in the 700 °C calcined silica glass at all measuring temperatures. The Cu 2+-pair/CuO cluster spectrum is absent. (iv) The isotropic EPR spectrum due to rapidly rotating Cu 2+-species occurring in very large pores of silica glass calcined at 800 °C has been obtained at room temperature. (v) Pore collapse starts at 900 °C, and results in the observance of a very broad EPR line (∼5000 Oe) for 900 and 1000 °C calcined samples. This shows that the pore collapse and the formation of superparamagnetic nano-sized CuO particles in the silica glass matrix take place simultaneously.

METROLOGICAL AND ALGORITHM MODEL FOR NANO-SCALE LINEWIDTH MEASUREMENTS USING AFM

Nano-scale linewidth measurements are widely performed in semiconductor manufacturing, data storage industry and micro-mechanical engineering. With the development of manufacturing technology in recent years, the sizes of linewidths are steadily shrinking and have been in the range of hundreds of nanometers. As a result, it is difficult to achieve accurate measurement results for nano-scale linewidth, because of the limitation of manufacturing technology and the influence of measuring instrument. In order to reduce the method divergences caused by different measurement methods and instruments for an accurate determination of nano-scale linewidth parameters, a metrological model and algorithm for linewidth measurements are established based on AFM measurements. The linewidth profile is divided into 5 parts with 19 sections and 20 key points and 6 accessorial points. Each section is fitted by a least squares straight line. According to the algorithm, bT and bTF, bM and bMF, bB and bBF represent the widths at the top, the middle and the bottom of the linewidth profile before and after the least squares fitting, respectively. AL and AR represent the left and right side-wall angles, and the h represents the step height of the linewidth profile. A NIST nano-scale linewidth standard developed at NIST's Electronics and Electrical Engineering Laboratory (EEEL) was measured using a commercial AFM with ultrasharp tips. The measured linewidth profiles are used for analyses using our model, algorithm and software. The results show that the model developed addresses the need of nano-scale linewidth metrology.

Strain and local heterogeneity in the forsterite?fayalite solid solution

Infrared powder-absorption spectra of nine natural and five synthetic olivine samples across the forsterite–fayalite join have been investigated at room temperature in the range 70–1400 cm−1. Variations of peak positions as a function of Fe content are close to linear for those vibrational bands whose trend could be followed across the solid solution. Line-broadening has been quantified by autocorrelation analysis. Positive deviations from linearity of the line-broadening parameter, Δcorr, for groups of bands at low energies are consistent with the existence of local elastic strain heterogeneities at intermediate compositions in the solid solution. It also appears that the structure of forsterite is more homogeneous than Fe-rich olivines in relation to local elastic strain effects. Positive deviations from linearity of the line-broadening parameter for the low-energy regions scale linearly with calorimetric data for the enthalpy of mixing. This close correlation between line-broadening in IR spectra and calorimetric enthalpies of mixing has now been observed for four different binary solid solutions, and there is a further, qualitative correlation with bulk modulus.

Solution-state dynamics of sugar-connected spin probes in sucrose solution as studied by multiband (L-, X-, and W-band) electron paramagnetic resonance

A multiband (L-band, 0.7 GHz; X-band, 9.4 GHz; and W-band, 94 GHz) electron paramagnetic resonance (EPR) study was performed for two glycosidated spin probes, 4-(α,β- d-glucopyranosyloxy)-TEMPO (Glc-TEMPO) and 4-(α,β- d-lactopyranosyloxy)-TEMPO (Lac-TEMPO), and one non-glycosylated spin probe, 4-hydroxy-TEMPO (TEMPOL), where TEMPO=2,2,6,6-tetramethyl-1-piperidinyloxyl, to characterize fundamental hydrodynamic properties of sugar-connected spin probes. The linewidths of these spin probes were investigated in various concentrations of sucrose solutions (0–50 wt%). The multiband approach has allowed full characterization of the linewidth parameters, providing insights into the molecular shapes of the spin probes in sucrose solution. The analysis based on the fast-motional linewidth theory has yielded anisotropy parameters of ρ x ≈ 2.6 and ρ y ≈ 0.9 for Glc-TEMPO, and ρ x ≈ 4.2 and ρ y ≈ 0.9 for Lac-TEMPO. These values indicate that the glycosidated spin probes have a prolate-type molecular shape elongated along the x-axis (NO axis) with Lac-TEMPO elongated more remarkably, consistent with their molecular structures. The interaction parameters k (the ratios of the effective hydrodynamic volumes to the real ones) corrected for the difference in molecular shape have been estimated and found to have the relation k(TEMPOL) < k(Glc-TEMPO) ≈ k(Lac-TEMPO). This agrees with the expectation that glycosidated spin probes can have stronger hydrogen bonding to water. Glycosidated spin probes are expected to be useful for probing sugar-involving interactions, which commonly occur in biological systems. Thus this study will provide an indispensable basis for such spin-probe studies.

Anisotropic motion effects in CW non-linear EPR spectra: relaxation enhancement of lipid spin labels

Continuous-wave (CW) EPR measurements of enhancements in spin–lattice ( T 1-) relaxation rate find wide application for determining spin-label locations in biological systems. Often, especially in membranes, the spin-label rotational motion is anisotropic and subject to an orientational potential. We investigate here the effects of anisotropic diffusion and ordering on non-linear CW-EPR methods for determining T 1 of nitroxyl spin labels. Spectral simulations are performed for progressive saturation of the conventional in-phase, first-harmonic EPR signal, and for the first-harmonic absorption EPR signals detected 90°-out-of-phase with respect to the Zeeman field modulation. Motional models used are either rapid rotational diffusion, or strong-jump diffusion of unrestricted frequency, within a cone of fixed maximum amplitude. Calculations of the T 1-sensitive parameters are made for both classes of CW-experiment by using motional parameters (i.e., order parameters and correlation times), intrinsic homogeneous and inhomogeneous linewidth parameters, and spin-Hamiltonian hyperfine- and g-tensors, that are established from simulation of the linear CW-EPR spectra. Experimental examples are given for spin-labelled lipids in membranes.

Atomic Physics Data for Stellar Atmospheres Research

The review will cover the following topics: (1) Ionization energies; (2) Partition functions; (3) Sources of data for atomic and ionic wavelengths, transition probabilities, and broadening parameters, including nuclear effects (hfs and isotope shifts); (4) Opacities from photoionization of abundant elements (atoms and atomic ions) with emphasis on integration of TOPBASE material; and (5) Data bases for diatomic molecules. We emphasize topics of direct relevance to the synthesis of stellar spectra, primarily within the domain where LTE is useful. Additional parameters, such as line-broadening parameters, or excitation cross sections are not reviewed.