Line Profile Parameters Research Articles

Collision parameters of N2-broadened methane lines in R5 multiplet of 2ν 3 band. Multispectrum fitting of overlapping spectral lines

The results of the investigation of absorption spectra of the methane R5 multiplet of 2ν 3 band, broadened by nitrogen, are presented. The absorption spectra of the methane-nitrogen mixture (CH4:N2 = 1:113.36) were recorded, using a two-channel photometric spectrometer, based on a tunable diode laser. The multispectrum least-squares fitting procedure was applied to all experimental spectra, recorded at different pressures, using the program, developed at IAO SB RAS (Protasevich, 2011). The program is based on a relatively simple line-profile model proposed in Pine (J. Quant. Spectrosc. Radiat. Transf. 57:145, 1997) and linear pressure dependence of the line-profile parameters. The line center positions, intensities, broadening, shifting, and mixing coefficients were determined for four lines of the methane R5 multiplet. The results have been compared with other available data.

Measurements of O 2-broadening and -shifting parameters of water vapor spectral lines in the second hexad region

Oxygen pressure induced broadening and shifting coefficients for water vapor absorption lines in the 8600–9010 cm −1 region have been measured and calculated. The spectra were recorded with a Bruker IFS 125HR spectrometer at a spectral resolution of 0.01 cm −1 for lines with angular moment of the upper states up to 10. Calculations of line broadening and shifting coefficients are performed using a semi-empirical approach. The method is based on the impact theory of broadening, and includes the correction factors whose parameters can be determined by fitting the broadening or shifting coefficients to the experimental data. The comparison of our calculations with the experimental values argues that the semi-empirical method is quite acceptable for the determination of the water vapor absorption line profile parameters.

Calculation of coefficients of collisional broadening of ozone spectral lines induced by pressure of atmospheric gases

Coefficients of the broadening of ozone lines by nitrogen and oxygen pressure in the ν1 + ν3 band at room temperature have been calculated. Calculations were performed by two methods. The first method is a modification of the semiclassical Robert-Bonamy formalism, in which parabolic trajectories are replaced by exact trajectories. This method enables one to describe the available experimental data with an accuracy of a few percents. The second, semiempirical, method is based on a two-parameter modification of the semiclassical impact model; it gives a high-accuracy global description of line profile parameters and, keeping the main physical regularities of pressure line broadening and shifting, enables a detailed study of these regularities and their dependence on environmental parameters. In contrast to the water vapor molecule, the broadening of spectral lines of the ozone molecule depends strongly on the rotational quantum numbers, so that the fitting parameters of the semiempirical method were determined separately for low, middle, and high values of the rotational quantum number J.

THE EXTRAGALACTIC DISTANCE DATABASE: ALL DIGITAL H I PROFILE CATALOG

An important component of the Extragalactic Distance Database (EDD) at http://edd.ifa.hawaii.edu is a group of catalogs related to the measurement of HI line profile parameters. One of these is the All Digital HI catalog which contains an amalgam of information from new data and old. The new data results from observations with Arecibo and Parkes telescopes and with the Green Bank Telescope (GBT), including continuing input since the award of the NRAO Cosmic Flows Large Program. The old data has been collected from archives, wherever available, particularly the Cornell University Digital HI Archive, the Nancay Telescope extragalactic HI archive, and the Australia Telescope archive. The catalog currently contains information on ~15,000 profiles relating to ~13,000 galaxies. The channel - flux per channel files, from whatever source, are carried through a common pipeline. The derived parameter of greatest interest is W_m50, the profile width at 50% of the mean flux. After appropriate adjustment, the parameter W_mx is derived, the linewidth which statistically approximates the peak to peak maximum rotation velocity before correction for inclination, 2 V_max sin(i).

Optically Forbidden Excitations of 2s Electron of Neon Studied by Fast Electron Impact

The electron energy loss spectrum in the energy region of 42-48.5 eV of neon is measured with an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of 2500 eV. Besides the dipole-allowed au-toionization transitions of 2s-1 np (n = 3,4) and 2p-2 3s3p, the dipole-forhidden ones of 2s-1 ns (n = 3 — 6) and 2s-1 3d are observed. The line profile parameters, i.e. Er, F and q for these transitions, are determined, and the momentum transfer dependence behaviour is discussed.

Line shape parameters study of the 6p7p (1P1, 3D1 and 3P1): Autoionizing resonances in barium

We report a systematic line shape analysis study of the 6p7p configuration based 1P1, 3D1 and 3P1 autoionizing resonances in barium using a Nd:YAG pumped dye laser system in conjunction with a thermionic diode ion detector. The even parity isolated autoionizing resonances have been approached via four intermediate states 6 snp 1P1 (6 ≤n ≤8) and 5d6p 1P1. A comparison of the Fano parameters of the resonance profiles reveals that the width of an autoionizing resonance is independent of the excitation path while the line profile parameter changes with the selection of different intermediate states.

The Advantage of Increased Resolution in the Study of Quasar Absorption Systems

We compare a new R = 120,000 spectrum of PG 1634+706 (zQSO = 1.337 and mV = 14.9) obtained with the HDS instrument on Subaru to a R = 45,000 spectrum obtained previously with the Keck HIRES. In the strong Mg II system at z = 0.9902 and the multiple-cloud, weak Mg II system at z = 1.0414, we find that at the higher resolution, additional components are resolved in a blended profile. We find that two single-cloud, weak Mg II absorbers were already resolved at R = 45,000, with b = 2-4 km s-1. The narrowest line that we measure in the R = 120,000 spectrum is a component of the Galactic Na I absorption, with b = 0.90 ± 0.20 km s-1. We discuss expectations of similarly narrow lines in various applications, including studies of damped Lyα absorbers, the Mg I phases of strong Mg II absorbers, and high-velocity clouds. By applying Voigt profile fitting to synthetic lines, we compare the consistency with which line profile parameters can be accurately recovered at R = 45,000 and 120,000. We estimate the improvement gained from superhigh resolution in resolving narrowly separated velocity components in absorption profiles. We also explore the influence of isotope line shifts and hyperfine splitting in measurements of line profile parameters, and the spectral resolution needed to identify these effects. Superhigh-resolution spectra of quasars, which will be routinely possible with 20 m class telescopes, will lead to greater sensitivity for absorption-line surveys, and to the determination of more accurate physical conditions for cold phases of gas in various environments.

Dispersion analysis of NiAl–TiC–Al 2O 3 composite powder ground in a high-energy attritorial mill

The NiAl–TiC–Al 2O 3 composite powder was prepared by self-propagating high-temperature synthesis (SHS) process using elemental powders as starting materials. As-prepared powder was ground by a high-energy attritorial mill for up to 40 h. The X-ray diffraction methods were used for the structure analysis of the as-prepared and ground samples. The Rietveld method was applied for the verification of the qualitative and quantitative phase composition of the studied material. The parameters of diffraction line profiles were determined by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed by Williamson–Hall method. It was found that during high-energy milling a significant decrease of crystallite size is observed only for NiAl phase. The crystallite size of this phase diminishes to 17 nm when the milling time rises to 40 h.

Analysis of an Inhomogeneous Semitransparent Plasma by the Lines in the Emission Spectrum

Using the methods of numerical simulation, we have investigated the dependence of the intensity and parameters of the spectral line profiles in the radiation of semitransparent plasma on its optical thickness, the degree of inhomogeneity, and the parameter distribution. As a model, we used the equilibrium plasma of argon with a given temperature profile on the observation line. The calculation has been performed for the spectral lines of the argon atom characterized by different broadening constants. On the basis of the results obtained it has been shown that it is possible to diagnose the plasma and determine the degree of its inhomogeneity and reabsorption by the parameters of the self-reversed profiles of the spectral lines. To diagnose the plasma in the absence of self-reversal, we propose to use the line intensities in the emission spectra of the plasma, including those obtained by probing it by its self-radiation.

Microstructure of Ni(Cr)–TiC–Cr 3C 2–Cr 7C 3 composite powder

The Ni(Cr)–TiC–Cr 3C 2–Cr 7C 3 composite powder was prepared by SHS (Self-propagating High-temperature Synthesis) process using elemental powders as starting materials. As-prepared powder was ground by an attritorial mill up to 10 h. Micrographs and diffraction patterns were obtained using TEM. The X-ray diffraction data were analyzed by the Rietveld method and Toraya procedure. The Rietveld method was applied in the determination of phase abundance using Hill and Howard approach. The parameters of diffraction line profiles were analyzed by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed using Williamson–Hall method. It was stated that the crystallite size of Ni(Cr) phase diminishes to nanoscale after 5 h milling whereas the crystallite size of the other phases is still above 100 nm for applied milling time.

Semi-empiric approach to the calculation of H2O and CO2line broadening and shifting

Abstract A semi-empiric approach to the calculation of spectral line half-widths and shifts is proposed. This approach is based on the Anderson approximation and includes the correction factors, the parameters of which can be determined by fitting the broadening or shifting coefficients to the experimental data. This allows sufficiently accurate predictions of the parameters of line profiles that were not measured. The coefficients of CO2 and H2O spectral line broadening and shifting due to air and nitrogen pressure are calculated, as well as the coefficients of their temperature dependence. The calculated coefficients agree satisfactorily with measured values.

Statistical comparison of transition region blinkers and explosive events

Explosive events and blinkers are two observational classes of transients seen on the quiet Sun and an investigation of the significance of and relationship between such events may be critical for understanding basic processes at work in the solar atmosphere. We analysed five time-series spectra of the quiet Sun of transition region O v 629 A, O VI 1032 A and O vi 1038 A lines. We investigated how often explosive events occurred during the course of a blinker at the same location and found that slightly more than a half of all explosive events happened during about one third of all blinkers. In some cases during a blinker more than one explosive event was registered. The largest average maximum relative intensity enhancement was for blinkers with explosive events, followed by the blinkers without explosive events, with the least being for the explosive events which did not happen during the course of a blinker. Due to these differences among the maximum enhancements between these events we suppose that blinkers and explosive events are two independent phenomena. Intensity light curves of blinkers show that events can be separated into two classes, specifically: 1) simple blinkers with smooth increase in intensity having only one significant peak, and 2) complex blinkers characterised by multiple (2-4) significant peaks. These two classes were equally represented when frequencies of their occurrences were averaged over five analysed data-sets. The analysis of the line profile parameters and their correlations for these two classes did not give any result which could further distinguish between them. During blinkers the intensity peaks mostly at the middle of their durations, while the line width peaks somewhat earlier than the intensity. This was a general character for both simple and complex blinkers, as well as for all explosive events.

E1−E2interference in the vuv photoionization of He

We have measured the forward-backward asymmetry of photoelectron angular distributions produced in the vacuum ultraviolet photoionization of helium. This asymmetry, a consequence of the breakdown of the dipole approximation, measures the real part of the ratio of the quadrupole and dipole matrix elements. In the autoionization region, the strong energy dependence of the asymmetry permits an experimental separation of the ratio of those magnitudes from their phase difference. We experimentally determined the Fano parameters of the ${2p}^{2}{}^{1}{D}_{2}$ quadrupole resonance, and report improved values of the width $\ensuremath{\Gamma}$ and line profile parameter q from those previously available from electron scattering. Off resonance, the smooth energy dependence of the asymmetry is found to agree well with the theoretical treatment presented here which incorporates higher-multipole effects.

Microstructure Analysis of Nanocrystalline Powders by X-ray Diffraction

The use of X-ray diffraction line profile analysis for the study of nanocrystalline powders is described. The fundamentals of the theory are presented in terms of crystallite/domain size, size distribution, lattice distortion, dislocation density and stacking faults. Line profile parameters and the methods of pattern fitting introduced to overcome the diffraction-line overlap problem are described. The approaches based of the integral breadth of the measured line profiles and the Fourier method are discussed. In addition, simplified approaches are also commented. Representative examples are selected to illustrate various cases of microstructure, such as nanomaterials with strain-free spherical nanocrystallites, strain-free crystallites with anisotropic crystallite shape, anisotropic crystallites with microstrains and spherical crystallites with dislocation densities and crystallite size distributions.

Hydrodynamical simulations of the Lyαforest: data comparisons

Numerical hydrodynamical simulations are used to predict the expected absorption properties of the Lyα forest for a variety of cold dark matter (CDM) dominated cosmological scenarios: CHDM, OCDM, ΛCDM, SCDM, and tCDM. Synthetic spectra are constructed duplicating the resolution, signal-to-noise ratio and wavelength coverage of several published high resolution spectra, and their statistical properties are compared on the basis of the flux distribution of the spectra, the distribution of coefficients in a wavelet decomposition of the spectra and the distributions of absorption line profile parameters. Agreement between the measured and predicted cumulative distributions is found at the few to several per cent level. The best-fitting models to the flux distribution correspond to normalizations on the scale of the cosmological Jeans length of at . No single model provides a statistically acceptable match to all the distributions. Significantly larger median Doppler parameters are found in the measured spectra than predicted by all but the lowest normalization models (CHDM and tCDM), which provide poor fits to the flux distributions. The discrepancy in Doppler parameters is particularly large for absorption systems optically thin at the Lyα line centre. This may indicate a need to introduce additional energy injection throughout the intergalactic medium, as may be provided by late He ii reionization or supernovae-driven winds from young galaxies, and/or a larger baryon fraction than given by recent determinations of the deuterium abundance within the context of standard Big Bang nucleosynthesis. The models require a hydrogen ionization rate at redshifts within a factor of 2 of that predicted from quasi-stellar objects (QSOs) alone as the sources of the UV photoionization background, although with a slower rate of decline with redshift at than predicted from current QSO counts. Principal systematic uncertainties in comparing the models with the observations are the setting of the continuum level of the QSO spectra and the prevalence of metal absorption lines, particularly at .

Comparison of Frequencies and Rotational Splittings of Solar Acoustic Modes of Low Angular Degree from Simultaneous MDI and GOLF Observations

During the years 1996 through 1998 the Michelson Doppler Imager (MDI) and the Global Oscillations at Low Frequency (GOLF) experiments on the Solar and Heliospheric Observatory (SOHO) mission have provided unique and nearly uninterrupted sequences of helioseismic observations. This paper describes the analysis carried out on power spectra from 759 days of calibrated disk-averaged velocity signals provided by these two experiments. The period investigated in this work is from 1996 May 25 to 1998 June 22. We report the results of frequency determination of low-degree (l ≤ 3) acoustic modes in the frequency range between 1.4 mHz and 3.7 mHz. Rotational splittings are also measured for nonradial modes up to 3.0 mHz. The power spectrum estimation of the signals is performed using classical Fourier analysis and the line-profile parameters of the modes are determined by means of a maximum likelihood method. All parameters have been estimated using both symmetrical and asymmetrical line profile-fitting formula. The line asymmetry parameter of all modes with frequency higher than 2.0 mHz is systematically negative and independent of l. This result is consistent with the fact that both MDI and GOLF data sets investigated in this paper are predominantly velocity signals, in agreement with previous results. A comparison of the results between the symmetric and asymmetric fits shows that there is a systematic shift in the frequencies for modes above 2.0 mHz. Below this frequency, the line width of the modes is very small and the time base of the data does not provide enough statistics to reveal an asymmetry. In general, the results show that frequency and rotational splitting values obtained from both the MDI and GOLF signals are in excellent agreement, and no significant differences exist between the two data sets within the accuracy of the measurements. Our results are consistent with a uniform rotation of the solar core at the rate of about 435 nHz and show only very small deviations of the core structure from the standard solar model.

SOHO Observations of the Connection Between Line Profile Parameters in Active and Quiet Regions and the Net Red Shift in EUV Emission Lines

We present high spatial and spectral resolution observations of one active and one quiet-Sun region, obtained with CDS and SUMER on SOHO. The connections between the line profile parameters are studied and a systematic wavelength shift towards the red with increasing peak line intensity (line broadening) is detected. The large scatter in the data calls for another approach. We apply conditional probability analysis to a series of EUV emission lines and find significant correlations between line profile parameters. For a given interval in wavelength shift we find that: (1) line profiles with large intensities (line widths) and red shifts above the average constitute an increasing fraction of the profiles as the relative wavelength shift increases, (2) line profiles with large intensities (line widths) and blue shifts compared to the average, on the other hand, constitute a decreasing fraction of the profiles as the relative wavelength shift increases. These results extend the findings of an earlier quiet-Sun study from one to several emission lines and expand the validity to include the active region. Interestingly, the active region observations show correlations between peak line intensity and wavelength shift in the coronal lines.

Density-functional theory with optimized effective potential and self-interaction correction for ground states and autoionizing resonances

We present a self-interaction-free density-functional theory (DFT) for the treatment of both the static properties of the ground states and the photoionization processes of many-electron systems. The method is based on the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential (OEP) theory and the incorporation of an explicit self-interaction correction (SIC) term. Such an extended OEP--KLI-SIC method uses only orbital-independent single-particle local potentials and is thus computationally more efficient and yet maintains good accuracy. The usefulness of the procedure is examined by the studies of the static properties of the ground states of atoms (Z\ensuremath{\leqslant}18) and the dynamical photoionization processes involving autoionizing resonances. Both the energy functionals of the local spin-density approximation (LSDA) and Becke's exchange energy functional and the correlation energy functional of Lee-Yang-Parr (BLYP) are used as the input to the KLI-SIC calculations. It is found that the implementation of the KLI-SIC procedure gives rise to optimized effective potentials that possess the correct behavior in both short-range and long-range regimes. As a consequence, the LSDA and BLYP ionization potentials are significantly improved. For higher-Z atoms, the improvement of the LSDA total energies and the ionization potentials are particularly remarkable, approaching the experimental or exact values. As another test of the KLI-SIC method, we have performed the calculation of the photoionization cross sections of the Ne atom using both the time-independent and time-dependent LSDA (TDLSDA) methods. We found that the TDLSDA results agree closely with the experimental data in the broad peak region, followed by a series of sharp resonances due to the 2s\ensuremath{\rightarrow}np resonant transitions. The calculated linewidths and resonance line profile parameters are in reasonable agreement with both the experimental and the configuration-interaction (R-matrix) results, demonstrating the usefulness of the KLI-SIC procedure for achieving accurate DFT calculations in both static properties and dynamical processes.

Spectra of High-Ionization Seyfert 1 Galaxies: Implications for the Narrow-Line Region

We present line profiles and profile parameters for the narrow-line regions (NLRs) of six Seyfert I galaxies with high-ionization lines: MCG 8-11-I1, Mrk 79, Mrk 704, Mrk 841, NGC 4151, and NGC 5548. The sample was chosen primarily with the goal of obtaining high-quality [Fe VII] λ6087 and, when possible, [Fe X] λ6374 profiles to determine if these lines are more likely formed in a physically distinct coronal line region" or are formed throughout the NLR along with lines of lower critical density (n_cr_) and/or ionization potential (IP). We discuss correlations of velocity shift and width with n_cr_ and IP. In some objects, lines of high IP and/or n_cr_ are systematically broader than those of low IP/n_cr_. Of particular interest, however, are objects that show no correlations of line width with either IP or n_cr_ In these objects, lines of high and low IP/n_cr_ are remarkably similar, which is difficult to reconcile with the classical picture of the NLR, in which lines of high and low IP/n_cr_ are formed in physically distinct regions. We argue for similar spatial extents for the flux in lines with similar profiles. Here, as well as in a modeling-oriented companion paper (Paper II), we develop further an idea suggested by Moore & Cohen that objects that do and do not show line width correlations with IP/n_cr_ can both be explained in terms of a single NLR model with only a small difference in the cloud column density distinguishing the two types of object. Overall, our objects do not show correlations between the full width at half- maximum (FWHM) and IP and/or n_cr_. The width must be defined by a parameter that is sensitive to extended profile wings in order for the correlations to result. In Paper II, we present models in which FWHM correlations with IP and/or n_cr_ result only after simulating the lower spectral resolution used in previous observational studies. The models that simulate the higher spectral resolution of our observational study produce line width correlations only if the width is defined by a parameter that is more sensitive to extended profile wings than is the FWHM. Our sample of six objects is in effect augmented by incorporating the larger sample (16 objects) of Veilleux into some of our discussion. This paper focuses on new interpretations of NLR emission-line spectra and line profiles that stem directly from the observations. Paper II focuses on modeling and complements this paper by illustrating explicitly the effects that spatial variations in electron density, ionization parameter, and column density have on model profiles. By comparing model profiles with the observed profiles presented here, as well as with those presented by Veilleux, Paper II yields insight into how the electron density, ionization parameter, and column density likely vary throughout the NLR.

Analytical dynamical models for double power-law galactic nuclei

Motivated by the finding that the observed surface brightness profile of many galactic nuclei are well fit by double-power-laws, we explore a range of spherical self-consistent dynamical models with this light profile. We find that the corresponding deprojected volume density profile, phase space density and line-of-sight velocity distribution of these models are well fit by simple analytic approximations. We illustrate the application of these models by fitting a sample of about 25 galactic nuclei observed by Hubble Space Telescope. We give the derived volume density, phase space density, velocity dispersion and line profile parameters in tables. The models are useful for predicting kinematic properties of these galaxies for comparison with future observations. They can also be easily applied to seed N-body simulations of galactic nuclei with realistic density profiles for studying the evolution of these systems.