Spectral Line Parameters Research Articles

Comparison of NH3 and 12CO, 13CO, C18O Molecular Lines in the Aquila Rift Cloud Complex

The observations of the Aquila Rift cloud complex at 23.708 and 115.271 GHz made using the Nanshan 26 m radio telescope and the 13.7 m millimeter-wavelength telescope are presented. We find that the CO(1 − 0) gas distribution is similar to the NH3 gas distribution in the Aquila Rift cloud complex. In some diffusion regions characterized by CO, we identified several dense clumps based on the distribution of detected ammonia molecular emission. Through the comparison of spectral line parameters for NH3, 13CO, and C18O, our study reveals that the line center velocities of the NH3, 13CO, and C18O lines are comparable and positively correlated, indicating that they originate from the same emission region. No significant correlation was identified for other parameters, including integrated intensity, line widths, main beam brightness temperature, as well as the column densities of NH3, 13CO, and C18O. The absolute difference in line-center velocities between the 13CO and NH3 lines is less than both the average line width of NH3 and that of 13CO. This suggests that there are no significant movements of NH3 clumps in relation to their envelopes. The velocity deviation is likely due to turbulent activity within the clumps.

Experimental and Theoretical Electron Collision Broadening Parameters for Several Ti II Spectral Lines of Industrial and Astrophysical Interest

A Q-switched Nd:YAG laser was focused on the Pb–Ti alloy samples in several laser-induced breakdown experiments in order to measure the Stark parameters of several spectral lines (58) of singly ionized titanium, including the 3504.89 Å and 3510.83 Å lines (where we achieved new experimental and theoretical values). The diagnostics of the laser-induced plasmas (electron density and electron temperature) were performed using Balmer’s H alpha line (6562.7 Å). The temperatures were obtained by the Boltzmann plot technique with spectral lines of Pb I (after correction for its evident self-absorption). Subsequently, the calculations by the Griem approach of the Stark broadening parameters for several spectral lines were performed using the Gaunt factors proposed by van Regemorter and those proposed by Douglas H. Sampson. In the latter case, the values obtained were very close to the experimental values. This enables us to assume that the calculations performed for the spectral lines of Ti II, without experimental information, are more accurate using the Gaunt factors proposed by Sampson.

CO2-broadened lineshapes in the oxygen A-band

High-resolution spectra of O2 broadened by CO2 pressure with high signal/noise ratio (2500 at the absorbance equal 1) were recorded with a Bruker IFS 125 FTIR spectrometer in the 13,000–13,260 cm−1 spectral region. The multispectrum fitting procedure has been applied to recover the spectral line parameters from measurements using the Voigt and speed-dependent Voigt (SDV) profiles. The O2 absorption line parameters for 40 transitions were measured. The parameters for SDV profile were studied for the first time. The uncertainty of the broadening coefficients for the unblended O2 absorption lines was estimated to be <3 %. The determined parameters were compared to HITRAN2020 and literature data. The values of the self-broadening coefficients and intensities were in good agreement with literature data.

Adaptive learning and expansion of spectral parameters in HITRAN database: A novel SCLB model for predicting high-temperature gas spectra

Recent advancements in aerospace optics have highlighted the significance of high-temperature gas optical radiation properties in the fields of optical research and optical detection. The High-Resolution Transmission Molecular Absorption Database (HITRAN) provides a comprehensive range of high-temperature gas spectral radiation parameters, which are essential for studying the optical radiation of these gases. However, the coverage of common gas spectral line parameters in the HITRAN database is insufficient, particularly in supporting the multi-spectral research in the burgeoning fields of aerospace optics and optical detection, especially in the ultraviolet range. This underscores the necessity of expanding the wavelength range of gas spectral parameters covered in the HITRAN database. In this study, we propose a physics-constrained LSTM-BPTransformer (SCLB) model that utilizes the distribution characteristics of gas spectral parameters in the database to predict spectral parameters for unknown wavelengths. The model combines data distribution quantification and distribution matching modules and incorporates the physical mechanisms of gas spectral radiation, thus enhancing prediction accuracy. Experimental results validate the effectiveness of the SCLB model, demonstrating that it can extend the data volume of gas spectral parameters in the HITRAN database by 4-5 times, while maintaining an error range within 1%. This predictive model enriches the research in high-temperature gas optics and lays a solid foundation for the application of high-temperature gases in the fields of optical research and optical detection.

Measurements and calculations of CO2-broadening and shift coefficients of water vapor transitions in the 5150–5550 cm−1 spectral region

The high-resolution H2O absorption spectra induced by CO2 pressure have been recorded using a Bruker IFS 125 HR FTIR spectrometer at room temperature in the 5150–5550 cm–1 spectral region. A multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters using the speed-dependent Voigt profile. The water vapor line broadening and shift coefficients for lines of two vibrational bands ν2+ν3 and ν1+ν2 were obtained. An uncertainty of the broadening coefficients for the unblended H2O absorption lines was estimated to be 2–3%. The calculations of line-broadening and line-shifting parameters were performed using the semi-empirical method which is based on the impact theory and enables a realistic prediction modified by introducing additional parameters obtained by using empirical data. The root mean square deviations of measured and calculated line widths and shifts were 0.0086 and 0.0053 cm−1 atm−1, respectively.

Measurements of air-broadening parameters of water vapour transitions in the 5090–7490 cm−1 spectral region

High-resolution spectra of H2O with a high signal/noise ratio (2500 at the absorbance equal 1) were recorded with a Bruker IFS 125 FTIR spectrometer covering H2O transitions from 5090 to 7490 cm−1 at the spectral resolution of 0.01 cm−1. The multispectrum fitting procedure has been applied to recover the spectral line parameters from measurements using quadratic speed-dependent Voigt (qSDV) profiles which made it possible to describe the experimental profile at the noise level. The H2 16O line broadening and shift coefficients for 439 lines of 7 vibrational bands 2ν3, ν2 + ν3, 2ν2 + ν3, ν1 + ν3, ν1 + ν2, ν1 + 2ν2 and 2ν1 were measured. A total of 339 lines were studied for the first time. The uncertainty of the broadening coefficients for the unblended H2O absorption lines was 2–4%. The determined parameters are compared to HITRAN12 and experimental values. The ratio between HITRAN data and our broadening coefficient varied from 0.82 to 1.21. The calculations of broadening and shift coefficients were performed in a framework of the semi-classical method and by using an empirical function whose parameters were taken from the literature. The uncertainty of calculations was 5% for the air broadening half-widths on average.

Theoretical and experimental study of inversion of spectral absorption function using experimental data of laser absorption spectrum with slow scanning and fast modulation of wavelength

Based on the tested data of laser absorption spectra, a matrix slicing method is proposed to invert the absorption function of spectral lines by using the two parameters of laser modulation frequency and laser scanning range as well as transmitted wave signal and reference wave signal under the condition of slow uniform scanning wavelength and fast periodic modulation wavelength. When the modulation is single frequency sinusoidal modulation, an accurate contour of the spectral line absorption function can be obtained by using the matrix data consisting of the values of the transmitted wave signal by the reference wave signal through the minimum value of two slice integrals with the interval of half modulation period, and the amplitude of modulation can be estimated. When the fast modulation of the wavelength is distorted to the multi-frequency superposition modulation, the absorption function is also formed by using the complementarity of multiple slices. The method above is utilized for investigating a real absorption function inversion process involving multiple overlapping absorption lines in the range of the scanning wavelengths. Moreover, the scanning range of laser wavelength can be calibrated by the interval parameters of several spectral lines in the scanning wavelength range. The absorption function of CO at 4300.700 cm&lt;sup&gt;–1&lt;/sup&gt; and CO&lt;sub&gt;2&lt;/sub&gt; at 6336 cm&lt;sup&gt;–1&lt;/sup&gt; are successfully obtained by using this matrix slice method for experimental verification.

Measurement of Rb isotope ratio by atomic absorption spectroscopy with multi-microchannel array structure cavity

Rubidium (Rb) isotope analysis has important applications in geological exploration and environmental detection. Based on tunable laser atom absorption spectroscopy technology combined with thermal decomposition of the sample, a Rb isotope absorption spectroscopy measurement device is built to detect the Rb isotope ratio stability. And the atomic generator is designed by a new micro-channel array structure, which enhances atomic beam collimation capability, effectively suppresses the doppler effect of the spectrum, and improves the resolution of Rb isotope absorption spectrum. The device adopts tantalum metal to make the atomic generator with a diameter of 6 mm, and the micro-channel array with a diameter of 1 mm is stacked inside the atomic generator which can be heated resistively to 3000 ℃. In this experiment, the Rb carbonate sample is catalyzed to release Rb atom beam at a high temperature of 600 ℃, while a probe laser is used to obtain high resolution Rb absorption spectrum. The Rb isotope ratio (&lt;sup&gt;85&lt;/sup&gt;Rb∶&lt;sup&gt;87&lt;/sup&gt;Rb) of natural abundance Rb carbonate samples is 2.441±0.02 by combining the inversion of the spectral line parameters, the detection error is 5.9%, and the detection limit of &lt;sup&gt;87&lt;/sup&gt;Rb is 1.76‰ (3&lt;i&gt;σ&lt;/i&gt;). The experimental results show that the multi-microchannel structure reduces the linewidth of Rb atoms by 450 MHz (half height full width) compared with the counterparts of the single-channel structure, which can effectively distinguish the absorption characteristics of Rb isotopes. The device has a high detection accuracy and a high spectral resolution, which provides a possibility for the metal isotope abundance analysis, and has a broad application prospect.

Water vapor absorption line parameters in the 6760–7430 cm–1 region for application to CO2-rich planetary atmosphere

The absorption spectra of the mixtures of water vapor and carbon dioxide at five different partial pressures of both gasses have been recorded using the Bruker IFS 125 HR FTIR spectrometer at room temperature in the 6760–7430 cm–1 spectral region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. To obtain the spectral lines parameters the quadratic speed-dependent Voigt profile was used. The water vapor line broadening and shift coefficients for lines of three vibrational bands ν1+ν3, 2ν2+ν3, and 2ν1 were obtained.

Irregular Spatial Distributions of Spectral Line Parameters in the Middle Solar Chromosphere Revealed from Analysis of Solar Flash Mg i b 2 Spectra

This paper presents the analytical results of solar Mg i b 2 flash spectra, obtained by the prototype Fiber Arrayed Solar Optic Telescope in process of the 2013 Gabon total solar eclipse. The analysis reveals irregular distributions of the spectral line parameters like ratio of line source function to continuum one β, ratio of line emissivity to continuum emissivity ζ, ratio of the continuum opacity to the line opacity r 0, line center optical depth τ 0, the line width Δλ D , and the line-of-sight velocity v los, while the approximately spherical symmetry can be found in the maps of integrated line intensity and continuum intensity. These irregular distributions originate from those of line profile features like the maximum intensity, the line width and line center wavelength. It is also found from the recovered line center optical depth τ 0 that in the middle chromosphere, the optical depth is not small due to non-ignorable absorption and the long light path along the line-of-sight. Finally, we show that the excessive broadening of spectral lines can be due to co-existence of multiple radiative sources with different line-of-sight velocities unresolved in one detector pixel.

Atomic data and opacity calculations in La v–x ions for the investigation of kilonova emission spectra

ABSTRACT A new set of radiative parameters for spectral lines in La v–x ions is reported in this paper. These data were determined through the use of a multiplatform approach involving three independent theoretical methods, i.e. the relativistic Hartree–Fock method including core-polarization corrections (HFR + CPOL), the multiconfiguration Dirac–Hartree–Fock (MCDHF) method, and the particle-hole configuration-interaction (PH-CI) method implemented in the AMBiT program. Based on cross-comparisons between the results obtained with these three methods, and from comparisons with the few previously published experimental and theoretical data, the most complete and reliable set of wavelengths, transition probabilities, and oscillator strengths was then used to determine the necessary opacities for the analysis of the spectra emitted in the early phases of kilonovae following neutron star mergers, i.e. for typical conditions corresponding to temperatures $T \gt 20\,000 $ K, a density ρ = 10−10 g cm−3, and a time after the merger t = 0.1 d.

Measurements of CO2-broadening and -shift parameters of the ethylene spectral lines near 3.3 µm

The absorption spectra of the mixtures of ethylene and carbon dioxide at seven different partial pressures of both gasses have been recorded using the Bruker IFS 125 HR FTIR spectrometer at room temperature in the 3.3 µm region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The broadening and shift coefficients induced in ethylene by carbon dioxide pressure have been obtained for almost 2000 lines in the region of the ν11 absorption band between 2928 and 3056 cm−1. The rotational dependence of the broadening parameters was analyzed. The similarity of the CO2-broadening coefficient to the self-broadening coefficient was revealed and discussed.

Simplified Theory of Line Broadening: Dependence of Spectral Line Parameters on Velocity and Temperature

Simplified Theory of Line Broadening: Dependence of Spectral Line Parameters on Velocity and Temperature

Shungite Carbon Nanoparticles as Modifiers of Zns:Cu Phosphor, Based on Analysis of the EPR Spectral Lines of Mn&lt;sup&gt;+2&lt;/sup&gt;

Water dispersions of shungite carbon (ShC) nanoparticles were used for modifying the particle surface of ZnS:Cu, commercial electrophosphor. The EPR spectrum of ZnS:Cu powder has parameters consistent with the paramagnetic centers of Mn+2. Modifying the phodphor surface with ShC nanoparticles results in a non-monotonic change in line width, amplitude and integral intensity caused by nanoparticle concentration, which correlates with variations in the brightness of electroluminescence. Variations in the parameters of spectral lines with nanoparticle concentration and UHF saturation power are interpreted in terms of modification and creation of additional dislocations in the subsurface layer of phosphor with new physico-chemical properties.

Spatially resolved spectroscopy across stellar surfaces

Context. High-precision stellar analyses require hydrodynamic 3D modeling. Testing such models is feasible by retrieving spectral line shapes across stellar disks, using differential spectroscopy during exoplanet transits. Observations were presented in Papers I, II, and III, while Paper IV explored synthetic data at hyper-high spectral resolution for different classes of stars, identifying characteristic patterns for Fe I and Fe II lines. Aims. Anticipating future observations, the observability of patterns among photospheric lines of different strength, excitation potential and ionization level are examined from synthetic spectra, as observed at ordinary spectral resolutions and at different levels of noise. Time variability in 3D atmospheres induces changes in spectral-line parameters, some of which are correlated. An adequate calibration could identify proxies for the jitter in apparent radial velocity to enable adjustments to actual stellar radial motion. Methods. We used spectral-line patterns identified in synthetic spectra at hyper-high resolution in Paper IV from 3D models spanning Teff = 3964–6726 K (spectral types ~K8 V–F3 V) to simulate practically observable signals at different stellar disk positions at various lower spectral resolutions, down to λ/Δλ = 75 000. We also examined the center-to-limb temporal variability. Results. Recovery of spatially resolved line profiles with fitted widths and depths is shown for various noise levels, with gradual degradation at successively lower spectral resolutions. Signals during exoplanet transit are simulated. In addition to Rossiter-McLaughlin type signatures in apparent radial velocity, analogous effects are shown for line depths and widths. In a solar model, temporal variability in line profiles and apparent radial velocity shows correlations between jittering in apparent radial velocity and fluctuations in line depth. Conclusions. Spatially resolved spectroscopy using exoplanet transits is feasible for main-sequence stars. Overall line parameters of width, depth and wavelength position can be retrieved already with moderate efforts, but a very good signal-to-noise ratio is required to reveal the more subtle signatures between subgroups of spectral lines, where finer details of atmospheric structure are encoded. Fluctuations in line depth correlate with those in wavelength, and because both can be measured from the ground, searches for low-mass exoplanets should explore these to adjust apparent radial velocities to actual stellar motion.

Empirical determination of atomic line parameters of the 1.5 μm spectral region

Context. Both the quality and amount of astrophysical data are steadily increasing over time owing to the improvement of telescopes and their instruments. This requires corresponding evolution of the techniques used for obtaining and analyzing the resulting data. The infrared spectral range at 1.56 μm usually observed by the GRegor Infrared Spectrograph (GRIS) at the GREGOR solar telescope has a width of around 30 Å and includes at least 15 spectral lines. Normally, only a handful of spectral lines (five at most) are used in studies using GRIS because of the lack of atomic parameters for the others. Including more spectral lines may alleviate some of the known ambiguities between solar atmospheric parameters. Aims. We used high-precision spectropolarimetric data for the quiet Sun at 1.56 μm observed with GRIS on the GREGOR along with the SIR inversion code in order to obtain accurate atomic parameters for 15 spectral lines in this spectral range. Methods. We used inversion techniques to infer both solar atmospheric models and the atomic parameters of spectral lines which, under the local thermodynamic equilibrium approximation, reproduce spectropolarimetric observations. Results. We present accurate atomic parameters for 15 spectral lines within the spectral range from 15 644 to 15 674 Å. This spectral range is commonly used in solar studies because it enables the study of the low photosphere. Moreover, the infrared spectral lines are better tracers of the magnetic fields than the optical ones.

Green Bank Telescope Observations of 3He+: Planetary Nebulae

Abstract We use the Green Bank Telescope to search for 3He+ emission from a sample of four Galactic planetary nebulae: NGC 3242, NGC 6543, NGC 6826, and NGC 7009. During the era of primordial nucleosynthesis, the light elements 2H, 3He, 4He, and 7Li were produced in significant amounts, and these abundances have since been modified primarily by stars. Observations of 3He+ in H ii regions located throughout the Milky Way disk reveal very little variation in the 3He/H abundance ratio—the “3He Plateau”—indicating that the net effect of 3He production in stars is negligible. This is in contrast to much higher 3He/H abundance ratios reported for some planetary nebulae. This discrepancy is known as the “3He Problem.” We use radio recombination lines observed simultaneously with the 3He+ transition to make a robust assessment of the spectral sensitivity that these observations achieve. We detect spectral lines at ∼1–2 mK intensities, but at these levels, instrumental effects compromise our ability to measure accurate spectral line parameters. We do not confirm reports of previous detections of 3He+ in NGC 3242 nor do we detect 3He+ emission from any of our sources. This result calls into question all reported detections of 3He+ emission from any planetary nebula. The 3He/H abundance upper limit we derive here for NGC 3242 is inconsistent with standard stellar production of 3He and thus requires that some type of extra-mixing process operates in low-mass stars.

Simplified theory of line broadening: dependence of spectral line parameters on speed and temperature

Simplified theory of line broadening: dependence of spectral line parameters on speed and temperature

The Formation of an Atypical Sunspot Light Bridge as a Result of Large-scale Flux Emergence

Abstract We use a combination of full-disk data from the Solar Dynamics Observatory and high-resolution data from the Dunn Solar Telescope (DST) to study the formation, structure, and evolution of an atypical light bridge (LB) in a regular sunspot. The LB results from the emergence of magnetic flux with one footpoint rooted in a pore outside the parent sunspot that appears about 17 hr before the LB. The pore has a polarity opposite to that of the sunspot and recedes from it at a speed of about 0.4 km s−1. This is accompanied by the development of an elongated magnetic channel in the outer penumbra that triggers the formation of the LB when it reaches the inner penumbral boundary. The LB is a nearly horizontal structure with a field strength of about 1.2 kG that exhibits long-lived photospheric blueshifts of about 0.85 km s−1 along its entire length. The emergence of the LB leads to dynamic surges in the chromosphere and transition region about 13 minutes later. We derive the photospheric and chromospheric structure of the LB in the DST data from spectral line parameters and inversions of He i at 1083 nm, Si i at 1082.7 nm, Ca ii IR at 854 nm, and H α at 656 nm and speckle-reconstructed imaging at 700 and 430 nm. The LB shows an elongated filamentary shape in the photosphere without lateral extrusions. The thermal inversion of Ca ii IR reveals the LB to be about 600–800 K hotter than the umbra. Different sections of the LB are elevated to heights between 400 and 700 km. Our results indicate that LB formation is part of a flux emergence event with the LB envelope reaching a height of about 29 Mm before dissolving after about 13 hr. We conclude that the existence of persistent, large-scale photospheric blueshifts in LBs is the most likely criterion for distinguishing between flux emergence events and overturning convection in field-free umbral intrusions.

Rotational Dependence of Line Halfwidth for the Fundamental Band 0 0 0 11–0 0 0 01 of CO2 Confined in Nanoporous Aerogel: New Measurements

The absorption spectra of carbon dioxide confined in an aerogel sample with pore sizes of 60 nm have been recorded at room temperature in the 2250–2400 cm−1 region using a Bruker IFS 125HR FTIR spectrometer. Parameters of spectral lines of CO2 are derived; their dependences on rotational quantum numbers are shown. The results are compared with data available in literature.