Line Profile Parameters Research Articles

Revisiting Jupiter's deuterium fraction in the rotational ground-state line of HD at high spectral resolution

The cosmic deuterium fraction, set by primordial nucleosynthesis and diminished by subsequent astration, is a valuable diagnostic tool to link the protosolar nebula to the history of star formation. However, in the present-day Solar System, the deuterium fraction in various carriers varies by more than an order of magnitude and reflects environmental conditions rather than the protosolar value. The latter is believed to be preserved in the atmospheres of the gas giant planets, yet determinations inferred from the CH$_3$D/CH$_4$ pair require a larger fractionation correction than those from HD/H$_2$, which are close to unity. The question of whether a stratospheric emission feature contaminates the absorption profile forming in subjacent layers was never addressed, owing to the lack of spectral resolving power. Here we report on the determination of the Jovian deuterium fraction using the rotational ground-state line of HD ($J=1-0$) at $ Employing the GREAT heterodyne spectrometer on board SOFIA, we detected the HD absorption and, thanks to the high resolving power, a weak stratospheric emission feature underneath; the former is blue-shifted with respect to the latter. The displacement is attributed to a pressure-induced line shift and reproduced by dedicated radiative-transfer modeling based on recent line-profile parameters. Using atmospheric standard models, we obtained $ D/H $, which agrees with a recent measurement in Saturn's atmosphere and with the value inferred from solar-wind measurements and meteoritic data. The result suggests that all three measurements represent bona fide protosolar D/H fractions. As a supplement and test for the consistency of the layering assumed in our model, we provide an analysis of the purely rotational $J=6-5$ line of CH$_4$ (in the vibrational ground state, at $ mu$m).

The pressure dependence of the experimentally-determined line intensity and continuum absorption of pure CO2 in the 1.6µm region

Fourier-transform measurements of pure CO2 spectra in the 1.6 µm region covering bands from the ground state to the 30011, 30012, 30013, and 30014 states at ambient temperature and 212 K with pressures up to 1 atm have been recorded. The measured spectra have been multispectrum-fitted with the Hartmann-Tran model with first order line-mixing taken into account. In the fits, a linear decrease of the line intensities with increasing pressure was introduced. From the fitted baselines, the self-continuum, which complements the contribution of the local lines within +/− 25 cm−1, was determined for the two strongest bands, 30012–00001 and 30013–00001. The depleted intensity was found to be transferred to the continuum for both temperatures. The intensity in the continuum at 1 atm was about 1 % of the total band intensity for ambient temperature and about 3 % at 212 K. For both temperatures, the average depleted intensity/continuum area was found in excellent agreement with values estimated from the second virial coefficient. From these results, a new spectroscopic database with pure CO2 line profile parameters was produced, with systematic line intensity uncertainties well below 0.1 %.Retrieval simulations for the CO2 1.6 µm and 2 µm bands measurements, planned with the future CO2M mission, similar to the OCO mission, were carried out to assess the impact of intensity depletion and continuum. The impact of the continuum was larger than that of the depletion and larger for the 2 µm band than for the 1.6 µm band, with a substantial column error of 2 % for the 2 µm band when omitting both, depletion and continuum.The findings regarding pressure-dependent intensity and continuum may be applicable to other in-band continua showing similarity to the monomer band in shape and position. The new results may increase the knowledge on the physical nature of continua.

The pressure effect on the line profiles observed in the [formula omitted] band of acetylene: Revisited

In our previous paper [K. Iwakuni et al., Phys. Rev. Lett.117, 1439026 (2018)] the ortho-para dependence of the pressure effects was reported for the ν1+ν3 band of acetylene measured by dual-comb spectroscopy. Sears and coworkers [E.C. Gross et al., J. Chem. Phys.154, 054305 (2021)] reevaluated the profile parameters for some lines of this band by comb-referenced laser spectroscopy, and pointed out that the ortho-para phenomenon must be a consequence of the use of Voigt function as the profile function, with the Doppler widths fixed at their theoretical values. Thus, we have remeasured this band with two improved spectrometers, the comb-locked laser spectrometer of the National Metrology Institute of Japan and another dual-comb spectrometer of Yokohama National University, and analyzed the lines by using the speed-dependent Voigt function as the profile function with several options. By the present work, we confirm the fact pointed out by Sears and coworkers, and present some remaining problems in the experimental determination of the line profile parameters.

A machine learning approach for correcting radial velocities using physical observables

Context. Precision radial velocity (RV) measurements continue to be a key tool for detecting and characterising extrasolar planets. While instrumental precision keeps improving, stellar activity remains a barrier to obtaining reliable measurements below 1–2 m s−1 accuracy. Aims. Using simulations and real data, we investigate the capabilities of a deep neural network approach to producing activity-free Doppler measurements of stars. Methods. As case studies we used observations of two known stars, ϵ Eridani and AU Microscopii, both of which have clear signals of activity-induced Doppler variability. Synthetic observations using the starsim code were generated for the observables (inputs) and the resulting Doppler signal (labels), and then they were used to train a deep neural network algorithm to predict Doppler corrections. We identified a relatively simple architecture, consisting of convolutional layers followed by fully connected layers, that is adequate for the task. The indices investigated are mean line-profile parameters (width, bisector, and contrast) and multi-band photometry. Results. We demonstrate that the RV-independent approach can drastically reduce spurious Doppler variability from known physical effects, such as spots, rotation, and convective blueshift. We identify the combinations of activity indices with the most predictive power. When applied to real observations, we observe a good match of the correction with the observed variability, but we also find that the noise reduction is not as good as in the simulations, probably due to a lack of detail in the simulated physics. Conclusions. We demonstrate that a model-driven machine learning approach is sufficient to clean Doppler signals from activity-induced variability for well-known physical effects. There are dozens of known activity-related observables whose inversion power remains unexplored, indicating that the use of additional indicators, more complete models, and more observations with optimised sampling strategies can lead to significant improvements in our detrending capabilities for new and existing datasets.

Effects of the chromospheric Lyα line profile shape on the determination of the solar wind H I outflow velocity using the Doppler dimming technique

Context. The determination of solar wind H I outflow velocity is fundamental to shedding light on the mechanisms of wind acceleration occurring in the corona. Moreover, it has implications in various astrophysical contexts, such as in the heliosphere and in cometary and planetary atmospheres. Aims. We aim to study the effects of the chromospheric Lyα line profile shape on the determination of the outflow speed of coronal H I atoms via the Doppler dimming technique. This is of particular interest in view of the upcoming measurements of the Metis coronagraph aboard the Solar Orbiter mission. Methods. The Doppler dimming technique exploits the decrease of coronal Lyα radiation in regions where H I atoms flow out in the solar wind. Starting from UV observations of the coronal Lyα line from the Solar and Heliospheric Observatory (SOHO), aboard the UltraViolet Coronagraph Spectrometer, and simultaneous measurements of coronal electron densities from pB coronagraphic observations, we explored the effect of the profile of the pumping chromospheric Lyα line. We used measurements from the Solar UV Measurement of Emitted Radiation, aboard SOHO, the Ultraviolet Spectrometer and Polarimeter, aboard the Solar Maximum Mission, and the Laboratoire de Physique Stellaire et Planetaire, aboard the Eight Orbiting Solar Observatory, both from representative on-disc regions, such as coronal holes and quiet Sun and active regions, and as a function of time during the solar activity cycle. In particular, we considered the effect of four chromospheric line parameters: line width, reversal depth, asymmetry, and distance of the peaks. Results. We find that the range of variability of the four line parameters is of about 50% for the width, 69% for the reversal depth, and 35% and 50% for the asymmetry and distance of the peaks, respectively. We then find that the variability of the pumping Lyα profile affects the estimates of the coronal H I velocity by about 9−12%. This uncertainty is smaller than the uncertainties due to variations of other physical quantities, such as electron density, electron temperature, H I temperature, and integrated chromospheric Lyα radiance. Conclusions. Our work suggests that the observed variations in the chromospheric Lyα line profile parameters along a cycle and in specific regions negligibly affect the determination of the solar wind speed of H I atoms. Due to this weak dependence, a unique shape of the Lyα profile over the solar disc that is constant in time can be adopted to obtain the values of the solar wind H I outflow velocity. Moreover, the use of an empirical analytical chromospheric profile of the Lyα, assumed uniform over the solar disc and constant in time, is justifiable in order to obtain a good estimate of the coronal wind H I outflow velocity using coronagraphic UV images.

An extended size–luminosity relation for the reverberation-mapped AGNs: the role of the accretion rate

ABSTRACT For a compiled sample of 120 reverberation-mapped AGNs, the bivariate correlations of the broad-line region (BLR) size (RBLR) with the continuum luminosity at 5100 Å (L5100) and the dimensionless accretion rates ($\dot{\mathscr {M}}$) are investigated. Using our recently calibrated virial factor f, and the velocity tracer from the H β full width at half-maximum (FWHM(H β)) or the line dispersion (σH β) measured in the mean spectra, three kinds of supermassive black hole (SMBH) masses and $\dot{\mathscr {M}}$ are calculated. An extended RBLR(H β)–L5100 relation including $\dot{\mathscr {M}}$ is found to be stronger than the canonical RBLR(H β)–L5100 relation, showing smaller scatters. The observational parameters, RFe (the ratio of optical Fe ii to H β line flux) and the line profile parameter DH β ($D_{\rm H\,\beta } =\rm FWHM(H\,\beta)/\sigma _{\rm H\,\beta }$), have relations with three kinds of $\dot{\mathscr {M}}$. Using RFe and DH β to substitute $\dot{\mathscr {M}}$, extended empirical RBLR(Hβ)–L5100 relations are presented. RFe is a better ‘fix’ for the RBLR(H β)–L5100 offset than the H β shape DH β. The extended empirical RBLR(H β)–L5100 relation including RFe can be used to calculate RBLR, and thus the single-epoch SMBH mass MBH. Our measured accretion rate dependence is not consistent with the simple model of the accretion disc instability leading the BLR formation. The BLR may instead form from the inner edge of the torus, or from some other means in which BLR size is positively correlated with accretion rate and the SMBH mass.

Measurements of N2-broadening and -shifting parameters of the water vapor spectral lines in the 19,560–19,920 cm−1 region using FT-spectrometer with LED source

The water vapor line broadening and shifting coefficients for about 91 strongest water vapor lines in the 19,560–19,920 cm−1 spectral region induced by nitrogen pressure are measured with a spectral resolution of 0.05 cm−1 at room temperature by a Fourier transform spectrometer using high luminance LED light source. A high signal-to-noise ratio (S/N ≈ 10 000) allows one to analyze the lines with intensities from 1.54 × 10−23 to 2.0 × 10−26 cm/molecule. The multi-spectrum fitting procedure was used to fit line broadening and shift parameters of the 5ν1+ν3, and 6ν1 bands using the Voigt, Speed dependent Voigt and HTP profiles. Line width and shift values are calculated using a semi-empirical approach extended by the use of empirical data to determine some fitting model parameters. The method was further developed by using anharmonic wavefunctions in the estimates of line profile parameters.

Dispersion and Structure Analysis of Nanocrystalline Ti-mZrO₂ Composite Powder for Biomedical Applications.

Titanium and titanium alloys are widely employed in biomedical applications but these alloys have unsatisfactory tribological properties because of their low hardness. Much better biomaterials for hard tissue replacement implants may be acquired by the preparation of titanium composites. Therefore, the connection of excellent biocompatibility and bioactivity of ZrO₂ ceramics with good properties of titanium is considered to be a promising approach for the fabrication of more perfect hard tissue replacement implants. This study describes the formation of Ti-ZrO₂ nanostructure composite biomaterial. Weighted amounts with the composition corresponding to Ti-xZrO₂ (x = 10, 30 and 50 wt.%) were high energy milled in the planetary ball mill PULVERISETTE 7 premium line by Fritch at 10, 30 and 50 h milling times. Structural evolution and morphological changes of the powder particles during mechanical alloying were studied using the X-ray diffractometer, scanning electron microscopy and transmission electron microscopy analysis. 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 to nanoscale is observed for α-Ti and mZrO₂ phases. The images from scanning and transmission electron microscopes of the milled powders show that the size of the agglomerates of Ti nanocrystallites changes in a broad range and that ZrO₂ particles can be immersed in larger agglomerates or occur separately.

Laboratory Hydrogen-Beta Emission Spectroscopy for Analysis of Astrophysical White Dwarf Spectra

This work communicates a review on Balmer series hydrogen beta line measurements and applications for analysis of white dwarf stars. Laser-induced plasma investigations explore electron density and temperature ranges comparable to white dwarf star signatures such as Sirius B, the companion to the brightest star observable from the earth. Spectral line shape characteristics of the hydrogen beta line include width, peak separation, and central dip-shift, thereby providing three indicators for electron density measurements. The hydrogen alpha line shows two primary line-profile parameters for electron density determination, namely, width and shift. Both Boltzmann plot and line-to-continuum ratios yield temperature. The line-shifts recorded with temporally- and spatially-resolved optical emission spectroscopy of hydrogen plasma in laboratory settings can be larger than gravitational redshifts that occur in absorption spectra from radiating white dwarfs. Published astrophysical spectra display significantly diminished Stark or pressure broadening contributions to red-shifted atomic lines. Gravitational redshifts allow one to assess the ratio of mass and radius of these stars, and, subsequently, the mass from cooling models.

Self-Broadening and Carbon-Dioxide Broadening of Lines of the H2S Molecule

Carbon-dioxide-broadening coefficients and self-broadening coefficients of lines of the main isotopic modification of Н2S are estimated on the basis of literature data. The J′-dependences of the above line-profile parameters of the hydrogen-sulfide molecule are examined. In the case of CO2 broadening, the half-widths of lines are calculated by a semiempirical method based on a parametric modification of the impact semiclassical model; the model parameters were determined from the fit to experimental data.

An empirical spectroscopic database for acetylene in the regions of 5850–6341 cm−1 and 7000–9415 cm−1

Six studies have been recently devoted to a systematic analysis of the high-resolution near infrared absorption spectrum of acetylene recorded by Cavity Ring Down spectroscopy (CRDS) in Grenoble and by Fourier-transform spectroscopy (FTS) in Brussels and Hefei. On the basis of these works, in the present contribution, we construct an empirical database for acetylene in the 5850–9415cm–1 region excluding the 6341–7000cm−1 interval corresponding to the very strong ν1+ν3 manifold. Our database gathers and extends information included in our CRDS and FTS studies. In particular, the intensities of about 1700 lines measured by CRDS in the 7244–7920cm−1 region are reported for the first time together with those of several bands of 12C13CH2 present in natural isotopic abundance in the acetylene sample.The Herman-Wallis coefficients of most of the bands are derived from a fit of the measured intensity values. A recommended line list is provided with positions calculated using empirical spectroscopic parameters of the lower and upper energy vibrational levels and intensities calculated using the derived Herman-Wallis coefficients. This approach allows completing the experimental list by adding missing lines and improving poorly determined positions and intensities. As a result the constructed line list includes a total of 11113 transitions belonging to 150 bands of 12C2H2 and 29 bands of 12C13CH2. For comparison the HITRAN database in the same region includes 869 transitions of 14 bands, all belonging to 12C2H2. Our weakest lines have an intensity on the order of 10–29cm/molecule, about three orders of magnitude smaller than the HITRAN intensity cut off. Line profile parameters are added to the line list which is provided in HITRAN format.The comparison of the acetylene database to the HITRAN2012 line list or to results obtained using the global effective operator approach is discussed in terms of completeness and accuracy.

HITRAN Application Programming Interface (HAPI): A comprehensive approach to working with spectroscopic data

The HITRAN Application Programming Interface (HAPI) is presented. HAPI is a free Python library, which extends the capabilities of the HITRANonline interface (www.hitran.org) and can be used to filter and process the structured spectroscopic data. HAPI incorporates a set of tools for spectra simulation accounting for the temperature, pressure, optical path length, and instrument properties. HAPI is aimed to facilitate the spectroscopic data analysis and the spectra simulation based on the line-by-line data, such as from the HITRAN database [JQSRT (2013) 130, 4–50], allowing the usage of the non-Voigt line profile parameters, custom temperature and pressure dependences, and partition sums. The HAPI functions allow the user to control the spectra simulation and data filtering process via a set of the function parameters. HAPI can be obtained at its homepage www.hitran.org/hapi.

The average energy difference method for calculation of line broadening of asymmetric tops

A new method for estimation of broadening coefficients of vibrational-rotational lines of asymmetric tops is presented. The method allows finding line widths on the basis of a few empiric data without complicated calculations. Based on the analysis of experimental data, the dependence of the average energy difference on vibrational quantum numbers is found. The approach has been tested by the example of calculation of line broadening of asymmetric tops H2O and HDO. Calculated parameters of line profiles were compared with experimental data in different absorption bands.

Fast-electron-impact study on excitations of 4d electron of xenon**Project supported by the National Natural Science Foundation of China (Grant Nos. U1332204, 11274291, 11504361, and 11320101003).

The electron energy loss spectrum of the 4d excitations of xenon was measured at an incident electron energy of 1500 eV and a scattering angle of 6°. Besides the optically allowed transitions of and the optically forbidden transitions of and were observed. The measured features are assigned with the help of the calculation by the Cowan Code. The line profile parameters of both optically allowed transitions and optically forbidden ones were determined and compared with the previous available data. It is found that the natural widths of both dipole-allowed and dipole-forbidden excitations are approximately identical, which means the spectator transitions dominate the resonant Auger effect for both dipole-allowed and dipole-forbidden transitions.

Dislocation Effects on the Diffraction Line Profiles from Nanocrystalline Domains

A Pd nano-polycrystalline microstructure was simulated by molecular dynamics, including edge or screw dislocations in one of the 50 grains, so as to produce a realistic model of nanocrystalline domain with line defect. The same crystalline domain was also studied, with or without line defects, as a free-standing, isolated nanocrystal. Atomic coordinates of the selected domain were used to generate powder patterns by means of the Debye scattering equation, and these patterns were used as “experimental” data to test existing methods of line profile analysis in controlled condition, i.e., with known type and density of defects. Results show that the Krivolgaz–Wilkens theory of dislocation line broadening qualitatively agrees with the MD model, but errors can be larger than 50 pct. A critical issue arises from the instability of the Krivolgaz–Wilkens model when all line profile parameters are simultaneously refined: reasonable results can be obtained by fixing or restricting some parameters.

Spectroscopic Variations of the Be-Shell Star EW Lacertae in the V/R Variation Periods

EW Lac showed remarkable $V/R$ variations in 1976–1986, and a similar $V/R$ variation started again in around 2007, after some quasi-periodic $V/R$ variations. For the first $V/R$ variation event, we analyzed the spectroscopic behaviors of emission lines and shell absorption lines of the Balmer series. The $V/R$ variations of the H$\alpha$ through H$\delta$ lines are characterized by the different manner of variations of the individual emission line in time lag and in duration of the $V/R$ phases. Weak correlation is also notable between the $V/R$ variations and other variations of the line-profile parameters, such as the peak velocities, emission-line intensities, and peak separations. We analyzed shell absorption lines for higher members of the Balmer series concerning their central depths and radial velocities. The optical depth of the H$\alpha$ line is in the range of 2000 to 6000, and its long-term variation discloses different behaviors as compared to the $V/R$ variations. Combining the analyses of emission and shell absorption lines, and regarding the $V/R$ variation as wave propagation phenomena, we find for the 1976–1986 event that the $V/R$ variation is of retrograde structure, and that a spiral structure is likely formed inside the disk in the latter half of this event. The weak correlations among physical parameters are suggestive of the disk being truncated at some radius. It is noticed that remarkable stellar brightening occurred in the latter half of the event, accompanying a marked decrease of the emission-line intensities. As for a $V/R$ variation that appeared in around 2007, which looks like a recurrence of a previous event, we found a less developed state of the disk without an appreciable time lag.

The fast rotating δ Scuti pulsator V376 Per: Frequency analysis and mode identification

AbstractOur simultaneous analysis of ground-based photometric and high-resolution spectroscopic data of the δ Scuti star V376 Per revealed eight individual frequencies from 82 nights of two-color photometry and six frequencies from the line-profile variations using 769 stellar spectra. Additionally, we identified the corresponding pulsation modes and derived reliable estimates of the line profile and pulsation mode parameters.

Dipole-quadrupole interference spectroscopy: Observation of an autoionizing He1DRydberg series

We have used dipole-quadrupole interference spectroscopy to observe an optically forbidden quadrupole Rydberg series of helium autoionizing levels. The technique measures the forward-backward asymmetry of photoelectron angular distributions produced in the vacuum ultraviolet photoionization of helium. The resonant behavior of this asymmetry in the region of a quadrupole autoionizing level enables the determination of the position, width, and Fano line-profile parameter $q$ of the level. We have obtained these quantities for the He ${}_{2}{(1,0)}_{n}^{+}{\phantom{\rule{0.28em}{0ex}}}^{1}\phantom{\rule{-0.16em}{0ex}}D$ Rydberg series for $n=2$--7. We find that for $n\ensuremath{\ge}3$ all three quantities have the expected $n$ scaling, with a quantum defect of 0.31. For $n\ensuremath{\ge}3$ the average $q$ parameter lies close to zero, whereas for $n=2$ it is negative.

Measurements and calculations of He-broadening and -shifting parameters of the water vapor transitions of the ν 1 + ν 2 + ν 3 band

The water vapor line broadening and shift in the ν 1 + ν 2 + ν 3 band induced by helium pressure were measured using a Bruker IFS 125HR FTIR spectrometer. The measurements were performed at room temperature at a spectral resolution of 0.01 cm−1 and in a wide He pressure range. The shifting coefficients δ are mainly positive, in contrast to the line center shift induced by other mono-atomic gases. Calculations of the coefficients γ and δ were performed in the framework of the semi-classical method. The influence of the rotational dependence of the isotropic intermolecular potential and accidental resonances in the H2O molecule on the shifting coefficients is discussed. Calculated values of line profile parameters are in a good agreement with observed parameters.

Collisional parameters of N2 broadened methane lines in the R9 multiplet of the 2ν3 band. Multispectrum fittings of the overlapping spectral lines

A high-sensitive two-channel photo-acoustic (PA) spectrometer with a near infrared diode laser was used to make precise measurements of N2-broadened methane spectra in the R9 multiplet of 2ν3 band. For the accurate retrieval of spectroscopic line parameters (intensities, positions at zero pressure, pressure-shifting and -broadening, collisional narrowing and line mixing coefficients) from the methane PA spectra, a program based on a multispectrum fitting procedure has been used. The multispectrum least squares fitting procedure is based on a relatively simple line profile model and on the linear pressure dependences of the line profile parameters. The line parameters were determined for 11 lines of the methane 2ν3 R9 multiplet. The results have been compared with other available data.