Search

Solar white-light flares are characterized by an enhancement in the optical continuum, which are usually large flares (X- and M-class flares). Here, we report a small C2.3 white-light flare (SOL2022-12-20T04:10) observed by the Advanced Space-based Solar Observatory and the Chinese H α Solar Explorer (CHASE). This flare exhibits an increase of ≈ 6.4% in the photospheric Fe i line at 6569.2 Å and ≈ 3.2% in the nearby continuum. The continuum at 3600 Å also shows an enhancement of ≈ 4.7%. The white-light bright kernels are mainly located at the flare ribbons and co-spatial with nonthermal hard X-ray sources, which implies that the enhanced white-light emissions are related to nonthermal electron-beam heating. At the bright kernels, the Fe i line displays an absorption profile that has a good Gaussian shape, with a redshift up to ≈ 1.7 km s−1, while the H α line shows an emission profile having a central reversal. The H α line profile also shows a red or blue asymmetry caused by plasma flows with a velocity of several to tens of km s−1. It is interesting to find that the H α asymmetry is opposite at the conjugate footpoints. It is also found that the CHASE continuum increase seems to be related to the change in the photospheric magnetic field. Our study provides comprehensive characteristics of a small white-light flare that help understand the energy release process of white-light flares. [ABSTRACT FROM AUTHOR]

The RNA world hypothesis suggests that early cellular ancestors relied solely on RNA molecules for both genetic information storage and cellular functions. RNA, composed of four nucleosides—adenosine, guanosine, cytidine, and uridine—forms the basis of this theory. These nucleosides consist of purine nucleobases, adenine and guanine, and pyrimidine nucleobases, cytosine and uracil, bonded to ribose sugar. Notably, carbonaceous chondrite meteorites have revealed the presence of these bases and sugar, hinting at the potential existence of nucleosides in space. This study aims to present the infrared spectra of four RNA nucleosides commonly found in terrestrial biochemistry, facilitating their detection in space, especially in astrobiological and astrochemical contexts. Laboratory measurements involved obtaining mid- and far-IR spectra at three temperatures (−180 °C, room temperature, and +180 °C), followed by calculating molar extinction coefficients (ε) and integrated molar absorptivities (ψ) for corresponding bands. These spectral data, along with ε and ψ values, serve to provide quantitative insights into the presence and relative abundance of nucleosides in space and aid in their detection. [ABSTRACT FROM AUTHOR]

The RNA world hypothesis suggests that early cellular ancestors relied solely on RNA molecules for both genetic information storage and cellular functions. RNA, composed of four nucleosides—adenosine, guanosine, cytidine, and uridine—forms the basis of this theory. These nucleosides consist of purine nucleobases, adenine and guanine, and pyrimidine nucleobases, cytosine and uracil, bonded to ribose sugar. Notably, carbonaceous chondrite meteorites have revealed the presence of these bases and sugar, hinting at the potential existence of nucleosides in space. This study aims to present the infrared spectra of four RNA nucleosides commonly found in terrestrial biochemistry, facilitating their detection in space, especially in astrobiological and astrochemical contexts. Laboratory measurements involved obtaining mid- and far-IR spectra at three temperatures (−180 °C, room temperature, and +180 °C), followed by calculating molar extinction coefficients (ε) and integrated molar absorptivities (ψ) for corresponding bands. These spectral data, along with ε and ψ values, serve to provide quantitative insights into the presence and relative abundance of nucleosides in space and aid in their detection.

Simultaneous observations of the Interface Region Imaging Spectrograph (IRIS) data, with a spatial resolution of less than one second consisting of ultraviolet (UV) spectra and images (SJI), make it possible to investigate solar chromosphere and transition region and provide valuable information about the dynamics of solar jets. IRIS combines numerical modeling, high resolution imaging, and UV spectroscopy. The interface region is the main place for the transfer of energy from the solar surface to the very hot corona. Of course, knowing the secret of energy transfer in the solar atmosphere is not the only goal of this mission, but also it examines the solar winds that is emitted from this area, which carry a rain of charged particles into space and also affect the Earth's climate. Information about the dynamic behavior of the physical phenomena of the solar atmosphere is obtained by studying the characteristics of spectral lines. For this purpose, it is necessary to obtain the information to identify and study spectral lines and how they are formed. The solar atmosphere is a plasma environment associated with a variety of transient events. Astrophysicists, especially in the field of solar dynamic physics, describe these events by magneto-hydrodynamics aspect. One of these phenomena is the bright spots of the solar atmosphere called jets. We identify and study the dynamics of a series of jets recorded on August 17, 2014, at Mg II k, C II and Si IV spectral lines corresponding to the 2796 A, 1336 A, and 1394 A wavelengths, respectively. Jets are small-scale dynamic events that can be detected by non-Gaussian profiles of lines in the solar chromosphere and transition region. The production mechanism of these plasma jets is still being investigated. We use the temporal evolution analysis method to track the path of these structures and determine their apparent velocity. To calculate the Doppler velocity we perform Gaussian fitting at the same time on the spectral intensity profiles. The apparent velocity results show that these jets have quasiperiodic motions with speeds of approximately 10 to 110 kms-1. Spectral investigation of these jets also shows the periodic behavior that is associated with increasing in blue and red wings at the three wavelengths as -65 to 40, 60 to 50, and 80 to 60 kms-1, respectively. Simultaneous enhancements in the blue and red wings of the spectrum can be caused by two-directional upward currents caused by magnetic reconnection and amplified by waves with p-modes (compression modes). According to these results, it is suggested that the fluctuations in these events with increasing on one side of the spectrum and both sides of the wing are signs of spiral and rotational motions, respectively. The results of this research show that by using the data of the IRIS Telescope, it is possible to identify and extract the physical components of jets at different wavelengths and identify their dynamic behavior. These specifications will help us better understand the stratification of the solar atmosphere and how heat and matter are transferred to the sun's surface and the effects of such transitions on the Earth's atmosphere. The application of this study will be the goal of space research and is very important in identifying space and Earth's climate. [ABSTRACT FROM AUTHOR]

An algorithm for generating quasi-harmonic self-oscillations with a uniformly widened spectral line is presented. The algorithm is based on the equation of motion of the Thomson-type DT-oscillator, which introduced a random effect in the form of band-pass white noise. Two types of effects are implemented: additive and parametric. Spectral characteristics of generated self-oscillations were analyzed by numerical experiment. The additive algorithm is shown to generate self-oscillations with amplitude-frequency fluctuations. Frequency fluctuations set the Lorentz (resonant) shape of the central part of the self-oscillation power spectrum, amplitude fluctuations form a noise pedestal of the spectral line. Based on the analysis of statistical characteristics of fluctuations in the frequency of the DT-oscillator with additive noise impact, a parametric algorithm for generating quasi-harmonic self-oscillations is proposed. In it, the resonance frequency of the oscillating system of the Thomson DT-oscillator is subject to random perturbations. The results of numerical experiments with generators of quasi-harmonic oscillations are given.

We study point-like explosive events (EE), characterized by emission in the far wings of spectral lines, in a quiet region near the South Pole, using Interface Region Imaging Spectrograph (IRIS) spectra at two slit positions, slit-jaw (SJ) observations, and Atmospheric Imaging Assembly (AIA) images. The events were best visible in Si iv spectra; they were weak in SJs, occasionally visible in 1600 Å and 304 Å AIA images, and invisible in higher temperature AIA images. We identified EEs from position–time images in the far wings of the Si iv lines and measured their distance from the limb. A Gaussian model of the height distribution showed that EEs occur in a narrow (0.9′′) height range, centered at 3.2′′ above the continuum limb at 2832.0 Å. On the disk, we found that they occur in network boundaries. Further, we studied the line profiles of two bright EEs above the limb and one on the disk. We found that what appears as broad-band emission is actually a superposition of 2 – 3 narrow-band Gaussian components with well-separated line profiles, indicating that material is expelled towards and/or away from the observer in discrete episodes in time and in space. The expelled plasma accelerates quickly, reaching line-of-sight (LOS) velocities up to 90 km s−1. Overall, the motion was practically along the LOS, as the velocity on the plane of the sky was small. In some cases, tilted spectra were observed that could be interpreted in terms of rotating motions of up to 30 km s−1. We did not find any strong absorption features in the wing of the Si iv lines, although in one case, a very weak absorption feature was detected. No motions indicative of jets were detected in SJ or AIA images. Reconnection in an asymmetric magnetic-field geometry, in the middle or near the top of small loops, is a plausible explanation of their observational characteristics. [ABSTRACT FROM AUTHOR]

The results of experimental studies of absorption spectra of pure NH3 in the 6604.3–6606.3 and 6611.6–6613.5 cm−1 ranges at room temperature and pressures of up to 0.04 atm are presented. The measurements were carried out at the Department of Diode Laser Spectroscopy of A.M. Prokhorov Institute of General Physics, Russian Academy of Sciences, in a high-sensitivity high-resolution diode laser spectrometer with a signal-to-noise ratio of ∼1400. The spectra are analyzed with the use of a Voigt profile. Parameters of spectral absorption lines are retrieved, including the line centers, intensities, and coefficients of collisional self-broadening and shifts, and compared with the parameters from the HITRAN database. A twofold difference between the measured intensities of a number of lines and the HITRAN values is found. [ABSTRACT FROM AUTHOR]

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Extreme ultraviolet Imaging Spectrometer (EIS) on board the Hinode spacecraft has been operating since 2006, returning high-resolution data in the 170 – 212 and 246 – 292 Å wavelength regions. EIS has four slit options, with the narrow 1′′ and 2′′ slits used for spectroscopy and the wide 40′′ and 266′′ slits used for monochromatic imaging. In this article several properties of the 40′′ slit (or slot) are measured using the Fe xii 195.12 Å line, which is formed at 1.5 MK. The projected width of the slot on the detector shows a small variation along the slit with an average value of 40.949′′. The slot image is tilted on the detector and a quadratic formula is provided to describe the tilt. The tilt corresponds to four pixels on the detector and the slot centroid is offset mostly to the right (longer wavelengths) of the 1′′ slit by up to four pixels. Measurement of the intensity decrease at the edge of the slot leads to an estimate of the spatial resolution of the images in the x -direction. The resolution varies quadratically along the slot, with a minimum value of 2.9′′ close to the detector center. Intensities measured from the slot images are found to be on average 14% higher than those measured from the 1′′ slit at the same spatial location. Background subtraction is necessary to derive accurate intensities in quiet-Sun and coronal-hole regions. Prescriptions for deriving accurate slot intensities for different types of slot datasets are presented. [ABSTRACT FROM AUTHOR]

In order to quantitatively analyze the proportions of independent components in mixtures, it is necessary to extract line spectra corresponding to those components from the spectrum signal of some mixture and evaluate the amplitude of the spectral lines. Multiple factors cause the drift and tilt of a spectrum signal's baseline, such as environment noises, instrument bias, and sample size, which affect the identification and quantitative analysis of the line spectra superimposed on the baseline. Therefore, the baseline of a spectrum signal should be removed before the line spectra are identified. A baseline correction algorithm based on Catastrophe Point detection and Lipschitz exponent's analysis is proposed in this paper. With the algorithm, the strong spectral lines are identified and removed, and then the spectral baseline is evaluated without the interference of strong spectrum signals. First, catastrophe points are located based on the local modulus maxima theory of wavelet coefficients. Second, according to the Lipschitz exponent theory, the strong spectral peaks' regions are identified and removed by a smoothing filter. Then the slowly varying spectrum is segmented adaptively and fitted by the least square fitting method. After the segments are attached and the boundaries are smoothed, the baseline of the spectrum is acquired and extracted finally. The algorithm is more accurate than classical ones because identifying the baseline is implemented after strong peaks are removed, so their influences to baseline extracting are eliminated. The results of experiments show that the algorithm is accurately performed for the spectrum signal of a gas mixture, S F 6 . [ABSTRACT FROM AUTHOR]

There are abundant emission and absorption lines superimposed on the continuum spectra of the different solar atmospheric layers. The chemical composition and physical state of the solar atmosphere can be probed by the inversion of the profiles of these spectral lines. Due to the low density and large temperature difference in the chromosphere and transition region of the Sun, it is hard to establish the thermal dynamic equilibrium. It is necessary to adopt the theory of Non-Local Thermodynamic Equilibrium (N-LTE) to construct the corresponding atmospheric model. In this paper, the departure from the Local Thermodynamic Equilibrium (LTE) in the middle and lower atmosphere of the sun is investigated with the well-defined relative departure factor and the relevant calculations. We first make an inversion of the spectral lines formed at the different heights in the chromosphere and transition region during a total solar eclipse, to obtain the parameters of the observed spectral lines, such as the continuum source function, line source function, Doppler width, and thus the equivalent kinetic temperature. According to these line parameters obtained by the inversion, we calculate the quantitative results about the departure from the LTE at each space sampling point in the 2D field of view. Secondly, we reconstruct the 2D distributions of the radiation intensity, equivalent kinetic temperature, and relative departure factor according to the alignment of the optical fiber array in the integrated field unit (IFU) used by the telescope. The results show that there is a stronger correlation in the distributions of the temperature and relative departure factor existed in local small regions, but without evident correlation with the distribution of radiation intensity. There is an obvious difference between the distributions of the equivalent temperature and relative departure factor derived from two spectral lines, which shows a strong structurization and complexity existed in some local small regions of the solar atmosphere, and provides a new perspective for us to further understand the physics of the middle and lower atmosphere of the Sun. [ABSTRACT FROM AUTHOR]

In this work, we discuss the theoretical background for calculating the Doppler effect for distant cosmic radio sources. For this approach, we developed a user-friendly efficient software based on the IAU SOFA astrometric library. Comparison with other software and services confirms its acceptable accuracy. [ABSTRACT FROM AUTHOR]

The technique for precise measurements of wavelengths in the range around 222 nm (45030 cm–1) has been presented. The reciprocal linear dispersion of the spectrometer was 0.529 Å/mm. The measurements were made in the second spectral order for a grating with 2400 lines/mm. Identification of emission lines of hollow cathode lamp (Fe) was made in the spectral range 4428…4452 Å. The wavelengths were measured for 32 identified lines in the spectrum. The mean square error of measurements is 0.0005 Å.

We have studied the intensity of the spectral lines for the main components in clay: Al I 309.4 nm, Al II 358.7 nm, Mg II 279.6 nm, Ti II 323.6 nm vs. the position of the object relative to the focus of the optical system when the samples are exposed to single laser pulses from a YAG:Nd3+ laser. We have determined the permissible ranges for positioning the object relative to the focus of the optical system (positive and negative defocusing) for which there is practically no change in the reproducibility of the intensity for the spectral lines for red and white clay samples. We show that the position of the object relative to the focus of the optical system should be within the range ΔZ ~ ±1.5 mm for optimal laser pulse energies for the analyte spectral lines. We have calculated the radiation flux density for different laser pulse energies and different distances from the focus to the object. We have shown experimentally that reducing the radiation flux density leads to a decrease in the intensity of the analyte spectral lines. [ABSTRACT FROM AUTHOR]

Based on the accumulated experiment experience and technology of Key Laboratory of Materials Modification by Laser, Ion and Electron Beams of Ministry of Education, a platform on laser induced breakdown spectroscopy (LIBS) is designed and constructed. In this work, the equipment module of the platform is presented; the operating technique and the parameter optimization are introduced. The pollution elements of heavy metals like Cu, Pb, Zn are selected as the subject investigated, the simulated detection on the sea water is carried out, the concentration of signal varied with strength of the LIBS are obtained, and the limitation of the detection for each element is given. Moreover, the samples from some sea area or drain outlet in Dalian city are collected, their pollution situations are analyzed. The results show that various metal ions in seawater samples can he analyzed on-line soon with this experiment system, and the great potential of LIBS technology in the field of liquid detection is revealed. [ABSTRACT FROM AUTHOR]

The M7.7 solar flare on July 19, 2012, is the most dramatic example of a 'Masuda' flare with a well-defined second X-ray above-the-loop-top source. The behavior of the system of loops accompanying this flare has been studied comprehensively by Liu et al. based on Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) data. We have performed spectroscopic and filter observations of the Hα loops in this flare with the Large Solar Vacuum Telescope. The basic physical parameters in the loops of this peculiar flare generally coincide with the known data in Hα loops. However, the electron density, 10 cm, and the integrated disk-center continuum intensity, 12%, are quite high, given that the observations were obtained almost 3 h after the flare onset.We have estimated the ascending velocity of the loop arcade (~3.5 km s) and the height difference between the Hα and 94 Å loops (~2 × 10 km). [ABSTRACT FROM AUTHOR]

The limiting short-term frequency instability of the output signal of a passive hydrogen frequency and time standard is calculated. A technique for experimental measurement of the figure of merit of a quantum discriminator is set forth. The frequency instability of the standard is estimated on the basis of the obtained data. The effect of spectral line splitting of a maser with increasing excitation signal discovered in the course of the study represents an obstacle against achieving any decrease in the instability of the standard. [ABSTRACT FROM AUTHOR]

We investigate the influence of the sea surface temperature (SST) changes on the middle atmosphere of a tidally locked Earth-like planet orbiting a G star using the coupled 3D chemistry-climate model CESM1(WACCM). We perform three 90 day simulations. The first simulation is a present-day Earth (PDE) simulation, the second is a simulation of a tidally locked Earth-like planet with a tidally locked aquaplanet sea surface temperature (cold TLE (CLTE)) and the third is a hybrid simulation of a tidally locked Earth-like planet with a present-day Earth sea surface temperature (warm TLE (WTLE)). Our results show that changes in the SST have an influence on the lower stratospheric temperature and the secondary ozone layer. Both atmospheres exhibit a dayside upwelling and a nightside downwelling extending from the surface to the mesosphere. They are also characterised by comparable lower and middle stratospheric horizontal winds and relatively different mesospheric horizontal winds. The temperature of the WTLE atmosphere is altered as a result of the SST changes, compared to the CTLE. Specifically, the WTLE lower tropospheric temperature is increased by 3.7 K on average, due to the absorption of the increased upwelling longwave radiation and the increased sensible and latent heat. The WTLE upper troposphere temperature is decreased by 4 K on average, is adiabatic in nature, and is generated by the increased WTLE upwelling. The WLTE lower stratospheric temperature is increased by 3.8 K on average due to the absorption of the increased upwelling longwave radiation. The lower mesospheric temperature is decreased by 1.13 K on average due to increased mesospheric wave breaking. The upper mesospheric temperature is increased by 4.3 K, and its generation mechanism is currently unknown. Furthermore, the secondary ozone volume mixing ratio is increased by 40.5 %. The occurrence of large-scale vortices and variable jet streams depends, to some extent, on the SST distribution. [ABSTRACT FROM AUTHOR]

The technique for precise measurements of wavelengths in the range around 222 nm (45030 cm-1) has been presented. The reciprocal linear dispersion of the spectrometer was 0.529 Å/mm. The measurements were made in the second spectral order for a grating with 2400 lines/mm. Identification of emission lines of hollow cathode lamp (Fe) was made in the spectral range 4428...4452 Å. The wavelengths were measured for 32 identified lines in the spectrum. The mean square error of measurements is ~0.0005 Å. [ABSTRACT FROM AUTHOR]

A comparison between a coronal hole (CH) and the adjacent quiet Sun (QS) has been performed using the spectroscopic diagnostics of the Hinode/EUV Imaging Spectrometer (EIS). Based on spectral signatures, we identify the coronal funnels that play an important role in the formation and propagation of the nascent fast solar wind. From the observed line profiles, we estimate the intensity, Doppler velocity, line width (FWHM), and electron density over CH and the adjacent QS region of a north polar coronal hole (NPCH). Excess-width regions (excess FWHM above a threshold level) have been identified in QS and CH. The plasma-flow inversion (average red-shifts changing to blue-shifts at a specific height) in CH and excess-width regions of QS take place at ${\approx}\,5.01\times10^{5}~\mbox{K}$. Furthermore, the high electron-density concentration in excess-width regions of QS provides an indication that these regions are the footprints of coronal funnels. We also find that non-thermal velocities of CH are higher in comparison to QS indicating that the CHs are the source regions of the fast solar wind. Doppler and non-thermal velocities, as recorded by different-temperature lines, have also been compared with previously published results. As we go from lower to the upper solar atmosphere, down-flows are dominant in the lower atmosphere, while coronal lines are dominated by up-flows with a maximum value of ≈ 10 - 12 km s in QS. The non-thermal velocity increases first but after $\log T_{e} = 5.47$ it decreases further in QS. This trend can be interpreted as a signature of the dissipation of Alfvén waves, while an increasing trend reported earlier may be attributed to the signature of the growth of Alfvén waves at lower heights. The predominance of the occurrence of nano-flares around the O vi formation temperature could also explain the non-thermal-velocity trend. [ABSTRACT FROM AUTHOR]

A new approach is presented in this paper to link optical emission spectrum analysis to the quality of clad layers produced with laser metal deposition (LMD). A Nd:YAG laser ( λ = 1.064 μm) was used to produce clad tracks with Metco 42C powder on AISI 4140 steel substrate. The laser power was ramped in steps of 220 W from 800 W to 2780 W focusing the laser beam into a 4.8 mm diameter spot. A constant cladding speed of 10 mm s −1 is used with a powder feeding rate of 0.36 g s −1 . The extent of metallic bonding is evaluated from dilution data obtained by measuring the melt depth in the substrate from cross sections of the clads. The spectra generated during the deposition process were collected with an optical spectrometer attached to the laser head. The discrete spectral lines from the collected spectra were identified from the NIST database as Fe I and Cr I lines. Two different spectral analysis methods were used, namely the calculation of the electron temperature T e and the intensity ratio IR. The electron temperature T e is computed from four discrete Cr I lines at 526.415, 529.827, 532.834, and 534.044 nm wavelength. The intensity ratio IR is a measure of the absorption of a discrete Fe I line at 588.91 nm. The analysis of the collected spectra indicates that onset and extent of metallic bonding can be detected with a spectrometer during the deposition process. A sudden decrease of the IR signal during the LMD process indicates the onset of metallic bonding. A further increase of the laser power mainly contributes to an increase in melt depth, leading to a higher dilution. In this region, the T e signal shows a better correlation with the dilution. [ABSTRACT FROM AUTHOR]

Using the path integral formalism, the fine structure and dynamics effects are taken into account for the study of the spectral line broadening in plasmas. A compact expression of the dipolar autocorrelation function (DAF) for an emitter in the plasma is derived for Lyman alpha lines with fine structure. The expression of the DAF takes into account the dynamics effects, which are represented by the time autocorrelation function of the electric microfield. The spectral line for the Lyman-alpha case has been obtained in a compact form and plotted in the quasi-static approximation and compared to a line obtained by a simulation. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The Multi-application Solar Telescope is a 50 cm off-axis Gregorian telescope that has been installed at the lake site of Udaipur Solar Observatory. For quasi-simultaneous photospheric and chromospheric observations, a narrow-band imager has been developed as one of the back-end instruments for this telescope. Narrow-band imaging is achieved using two lithium niobate Fabry-Perot etalons working in tandem as a filter. This filter can be tuned to different wavelengths by changing either voltage, tilt, or temperature of the etalons. To characterize the etalons, a Littrow spectrograph was set up in conjunction with a 15 cm Carl Zeiss Coudé solar telescope. The etalons were calibrated for the solar spectral lines Fe i 6173 Å, and Ca ii 8542 Å. In this work, we discuss the characterization of the Fabry-Perot etalons, specifically, the temperature and voltage tuning of the system for the spectral lines proposed for observations. We present the details of the calibration set-up and various tuning parameters. We also present solar images obtained using the system. [ABSTRACT FROM AUTHOR]

Atomic spectroscopy experiments have reached a level where the transition line profile has become measurable with high precision. One of the most important task of such experiments is the determination of the transition frequency and an accurate comparison with the corresponding theoretical value. However, a detailed theoretical description of the line profile requires consideration of increasingly tiny effects which can play a crucial role in determining fundamental physical constants. In particular, it was shown recently that the nonresonant corrections arising in the description of the scattering processes of photon by atoms can lead to significant changes in the determination of the transition frequency. In present work, an adaptive method of moments for extracting the transition frequency from the experimental spectral data is discussed. • Typically, the transition frequency is determined by the maximum of the line shape. • The choice of line shape for fitting depends on the processes under consideration. • Alternatively, the method of moments is used for this purpose. • The advantages and disadvantages of the adapted method of moments are discussed. • The application of the method to experimental data is given in the work. [ABSTRACT FROM AUTHOR]

In theory of the spectral line shapes, the conventional scheme use two approximations for the local electric field (microfield) due to all charged particles of the plasma. The quasi-static approximations for the ions and the impact approximation for the electrons. The first approximation consists to say that the electric field is constant during the characteristic time. In this work we shall transpose the idea of the first approximation, to the angular velocity of the microfield whereas its strength is kept constant and equal to its mean value. We shall use the Holtsmark approach and the independent particles model (due to Margeneau and Lewis) to compute the static distribution function of the angular velocity of the microfield. In the first approach (Holtsmark), the distribution shows a Lorentzian behavior, whereas the second approach (Margenau and Lewis) shows a gaussian behavior. Subsequently, we have applied the obtained static distribution to show the effect on the broadening of Lyman-alpha line for a plasma composed of He+ ions. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a list of 61 solar photospheric lines in the near-infrared H-band (1500 – 1800 nm), obtained by synthesis under the LTE approximation, and compute the corresponding velocity and temperature response functions (RF) in the line core and depth-integrated RFs as a function of wavelength. In particular, we computed the core formation heights and the ranges of atmospheric layers where thermodynamic perturbations are dominant. Moreover, we indicate the wavelength where the line is more sensitive to thermodynamic variations and quantify this sensitivity. This list is the extension of a previous work of Penza and Berrilli ( Solar Phys.277, 227, 2012 ). [ABSTRACT FROM AUTHOR]

Highlights: [•] High-lying values of spectral lines of rovibrational transition are important. [•] Those values are difficult to obtain experimentally or quantum mechanically. [•] Analytical formula which are proposed to predict the values in our previous work. [•] This study generates correct data of NbN. [•] Supplies a reliable and economical physical method theoretically. [ABSTRACT FROM AUTHOR]

We present a new list of solar photospheric lines in the near-infrared (NIR) region obtained by synthesis under local thermodynamic equilibrium (LTE) approximation. We give novel velocity and temperature response functions (RFs) for 77 lines over the spectral range 800 - 1400 nm. Using these RFs, we are able to obtain for each line the core formation height and the range of atmospheric layers where thermodynamic perturbations are dominant. Moreover, by using the depth-integrated RFs, we give an indication of the dependence on the wavelength of the RFs and quantify their sensitivity to thermodynamic variations. The NIR region represents a significant source of interest for spectroscopic and polarimetric studies. Indeed, at these wavelengths we explore the deeper photospheric layers, and the Zeeman splitting is larger than in the visible range. Several research fields in solar astrophysics ( e.g., photospheric and chromospheric dynamics, magnetoconvection in active regions, and interaction between solar plasma and magnetic field) should benefit from using this new line list. Moreover, various new NIR instruments are planned for future space missions or next generation ground-based solar telescopes, such as the European Solar Telescope (EST) or the Advanced Technology Solar Telescope (ATST). [ABSTRACT FROM AUTHOR]

Spontaneous emission in a four-level atomic system coupled by two coherent driven fields is investigated. Using a wave function technique, an explicit expression of the spontaneous emission spectrum is derived. The influence of driven fields on spontaneous emission spectra of k and q photons are investigated. The interesting phenomena including spectral line narrowing, enhancement, suppression and quenching, are observed by adjusting driven fields and detunings. [ABSTRACT FROM PUBLISHER]

Abstract: An analytical formula is used to predict the accurate P-branch spectral lines of rovibrational transitions for diatomic systems. The formula is derived from elementary expression of molecular total energy by taking multiple spectral differences. It is not only reproduces the known experimental transition lines by using a group of fifteen known experimental transition data, but also predicts the accurate spectral lines that may not be available experimentally. The P-branch emission spectra of the (0,1), (0,2) and (0,3) bands of the B 2 ∑ + → X 2 ∑ + system in the 12C17O+ molecular ion are studied, and correct values of the unknown spectral lines up to J =80.5 for each band are predicted using the formula. [Copyright &y& Elsevier]

We performed two-dimensional spectroscopic observations of the preceding sunspot of NOAA 10905 located off disk center (S8 E36, μ≈0.81) by using the Interferometric BI-dimensional Spectrometer (IBIS) operated at the Dunn Solar Telescope (DST) of the National Solar Observatory, New Mexico. The magnetically insensitive Fe I line at 709.04 nm was scanned in wavelength repetitively at an interval of 37 s to calculate sequences of maps of the line-wing and line-core intensity, and the line-of-sight Doppler velocity at different line depths (3% to 80%). Visual inspection of movies based on speckle reconstructions computed from simultaneous broadband data and the local continuum intensity at 709.04 nm revealed an umbral dot (UD) intruding rapidly from the umbral boundary to the center of the umbra. The apparent motion of this object was particularly fast (1.3 km s) when compared to typical UDs. The lifetime and size of the UD was 8.7 min and 240 km, respectively. The rapid UD was visible even in the line-core intensity map of Fe I 709.04 nm and was accompanied by a persistent blueshift of about 0.06 km s. [ABSTRACT FROM AUTHOR]

We present the application of novel diagnostics to the spectroscopic observation of a Coronal Mass Ejection (CME) on disk by the Extreme Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. We apply a recently developed line profile asymmetry analysis to the spectroscopic observation of NOAA AR 10930 on 14 – 15 December 2006 to three raster observations before and during the eruption of a 1000 km s−1 halo CME. We see the impact that the observer’s line-of-sight and magnetic field geometry have on the diagnostics used. Further, and more importantly, we identify the on-disk signature of a high-speed outflow behind the CME in the dimming region arising as a result of the eruption. Supported by recent coronal observations of the STEREO spacecraft, we speculate about the momentum flux resulting from this outflow as a secondary momentum source to the CME. The results presented highlight the importance of spectroscopic measurements in relation to CME kinematics, and the need for full-disk synoptic spectroscopic observations of the coronal and chromospheric plasmas to capture the signature of such explosive energy release as a way of providing better constraints of CME propagation times to L1, or any other point of interest in the heliosphere. [ABSTRACT FROM AUTHOR]

We analyze EUV spectra of the full solar disk from the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The observations were obtained via a fortuitous off-axis light path in the 140 – 275 Å passband. The general appearance of the spectra remained relatively stable over the two-year time period, but did show significant variations of up to 25% between two sets of Fe lines that show peak emission at 1 MK and 2 MK. The variations occur at a measured period of 27.2 days and are caused by regions of hotter and cooler plasma rotating into, and out of, the field of view. The CHIANTI spectral code is employed to determine plasma temperatures, densities, and emission measures. A set of five isothermal plasmas fit the full-disk spectra well. A 1 – 2 MK plasma of Fe contributes 85% of the total emission in the CHIPS passband. The standard Differential Emission Measures (DEMs) supplied with the CHIANTI package do not fit the CHIPS spectra well as they over-predict emission at temperatures below log 10 T=6.0 and above log 10 T=6.3. The results are important for cross-calibrating TIMED, SORCE, SOHO/EIT, and CDS/GIS, as well as the recently launched Solar Dynamics Observatory. [ABSTRACT FROM AUTHOR]

A search has been carried out for the presence of rotational lines of two bands of the (0, 0) and (1, 1) A 1Π – X 1Σ+ system of the AlH molecule in the high resolution Fourier Transform Spectra of sunspots observed at the National Solar Observatory at Kitt Peak. Though the presence of the AlH molecule in sunspots was confirmed by Wallace, Hinkle, and Livingston (An Atlas of Sunspot Umbral Spectra in the Visible from 15 000 to 25 000 cm−1 (3920 to 6664 Å), Tech. Rep. 00-001, National Solar Observatory, Tucson, AZ, ), there is no report on the rotational temperature in the literature by identifying AlH molecular lines. The results obtained in this new search using a suitable identification technique are compared with the results reported by Wallace, Hinkle, and Livingston (). In view of the fact that the rotational temperatures of the molecules could be used to test photospheric and sunspot models, the effective rotational temperature for the (0, 0) band of the A – X system of AlH molecule is estimated by measuring the equivalent widths of well resolved spectral lines and its value justifies the existence of the AlH molecule in sunspots. [ABSTRACT FROM AUTHOR]

We study the selective reflection of the laser beam from rubidium atomic vapor at the D2 line (wavelength λ = 780 nm) at different atomic densities. We use a tunable free-running diode laser. We observed a measurable signal at a low atomic density N when the mean distance between resonance atoms reached two wavelengths. In our experiment, the dimensionless parameter N1 /3 λ varied from 0.5 to 2.8. The reflectivity increased with density monotonically. It is interesting to perform experiments when the parameter N1 /3 λ ≪ 1. [ABSTRACT FROM AUTHOR]

Digital image processing converts the digital images into spectral lines. According to the difference of the spectral line of wool and cashmere, six features are extracted from the spectral lines. With the comparison of the probability of the distributing graphs and the analysis of correlation of the six features, features of mean of the cross section and dispersion of the longitudinal direction are used to generate the discriminant function to identify wool and cashmere. Final result shows that it is an effective method in distinguishing cashmere from wool. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to show that the output from a double-output laser cavity exhibits distinctive features, manifesting themselves through typical asymmetry in the corresponding spectral-line shapes. Such asymmetry in an inhomogeneously broadened gas laser usually appears with a clear, but unpredictable shift of the maximum intensity level either towards the high or low frequency sides with respect to line centre. In the case of a double-output laser, the spectral profiles show opposite shifts. This means that when the maximum intensity of one output moves towards the high frequency side of the profile, the maximum intensity of the other moves towards the low frequency side. This gives rise to a frequency shift with respect to the Lamb-dip for a classical laser. On the theoretical side, we apply the standard disturbed Gaussian beam model to provide a quantification of the frequency shifts obtained at both sides of the system. [Copyright &y& Elsevier]

The flash spectra in the HeI D3 line were obtained during the 2008 total solar eclipse. This paper describes the instrument and the calibration of the obtained flash spectrum, and presents our initial results. The average integrated intensity is Eave = 8.13 × 1013 erg·cm−1·s−1·ster−1 at h = 1100 km, which confirms that the HeI D3 emission is negatively correlated with the solar activity. The surface brightness reaches a maximum of Fave = 8.25×105 erg·cm−2·s−1·ster−1 at about h ≈ (1290 ± 75) km and then decreases exponentially with height when h > 1800 km with an exponential index β = 1.63×10−8 cm−1. [ABSTRACT FROM AUTHOR]

Abstract: The potentials of two advanced laser-induced breakdown spectroscopy (LIBS) techniques which are used to determine the total carbon content in soils have been examined. The first one is the combination of a single-pulse laser ablation with spark excitation of plasma plume triggering the gap between electrodes close to the target surface. The second one is a more conventional double-pulse LIBS. In both modes the calibration graphs have a nonlinear trend in the actual range of carbon contents and present a good R 2 value (0.97). In the combined laser-spark approach, using low-cost and portable laser instrumentation is possible, as well as inducing a micro-damage on the target surface. Certain regularities in the spectral line intensities of soil nutritious elements have been detected and appear to be connected to the total carbon content and to the soil origin. [Copyright &y& Elsevier]

Abstract: A comparison of the atmospheric absorption calculated with different data banks of water vapour absorption lines is made. The HITRAN database, Barber-Tennyson line list (BT2), calculation of Partridge and Schwenke (PS) are considered. The contribution of H2O lines, absent in HITRAN, to the atmospheric transmission, calculated with 10cm−1 spectral resolution in the 10000–20000cm−1 spectral region is up to 1.5% for a vertical path and 4% for a solar zenith angle of 70deg. The highest difference is observed in the 940nm band. The incoming fluxes of solar radiation, measured by a rotating solar spectroradiometer, were modeled with BT2 and HITRAN database. The difference between measured and calculated fluxes does not exceed the instrumental uncertainties. [Copyright &y& Elsevier]

The properties of solar magnetic fields on scales less than the spatial resolution of solar telescopes are studied. A synthetic infrared spectropolarimetric diagnostic based on a 2D MHD simulation of magnetoconvection is used for this. Analyzed are two time sequences of snapshots that likely represent two regions of the network fields with their immediate surroundings on the solar surface with unsigned magnetic flux densities of 300 and 140 G. In the first region from the probability density functions of the magnetic field strength it is found that the most probable field strength at log τ 5=0 is equal to 250 G. Weak fields ( B<500 G) occupy about 70% of the surface, whereas stronger fields ( B>1000 G) occupy only 9.7% of the surface. The magnetic flux is −28 G and its imbalance is −0.04. In the second region, these parameters are correspondingly equal to 150 G, 93.3%, 0.3%, −40 G, and −0.10. The distribution of line-of-sight velocities on the surface of log τ 5=−1 is estimated. The mean velocity is equal to 0.4 km s−1 in the first simulated region. The average velocity in the granules is −1.2 km s−1 and in the intergranules it is 2.5 km s−1. In the second region, the corresponding values of the mean velocities are equal to 0, −1.8, and 1.5 km s−1. In addition the asymmetry of synthetic Stokes V profiles of the Fe i 1564.8 nm line is analyzed. The mean values of the amplitude and area asymmetry do not exceed 1%. The spatially smoothed amplitude asymmetry is increased to 10% whereas the area asymmetry is only slightly varied. [ABSTRACT FROM AUTHOR]

The extended crossed-beam method has been used to study excitation of high-lying levels in the tungsten atom. 40 excitation cross sections of WI spectral lines have been measured for exciting electron energy 50 eV. Two optical excitation functions were recorded in the electron energy range 0–200 eV. The results obtained were used to calculate the total excitation cross sections of 24 odd WI energy levels. [ABSTRACT FROM AUTHOR]

Abstract: Space-, time- and spectrally resolved optical diagnostics of laser ablation plasma has provided the opportunity to realize calibration-free analyses of solid materials. In general, this variant of optical emission spectroscopy of pulsed plasma allows the plasma matrix effects to be overcome, yielding satisfactorily precise and accurate quantitative results on elemental composition of materials without using calibration curves, certified reference materials, and internal standards. Such analysis is very close to be nondestructive due to the minimum possible ablated mass, a feature which is very important in many applications, especially for unique museum exhibits and jeweler samples. In this paper, the use of the method for the analysis of elements in bronze, brass and gold alloys, glass samples, and archaeological findings is demonstrated. The results presented confirm the suitability of the approach for routine applications of our instrumentation, while at the same time simplifying the overall analytical procedure. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: This work presents the first report of uranium spectra generated by a low power microwave plasma source to conduct emission measurements. Distinct uranium peaks in the wavelength range examined from 320 to 430nm have been successfully obtained with a 200W plasma utilizing low gas flow rates. The influence of temperature on the uranium behavior in the plasma source is discussed, and the intensity of the spectral lines obtained with this low power source is systematically compared with the results reported in literature, in which high power plasma sources were employed. Concentration effects are studied and the calibration curves are made for some strong spectral lines. The detection limits of uranium are also estimated to be at the 0.4ppm level, with linear dynamic range at least two and half orders of magnitude. This research establishes a method to effectively generate uranium atoms and ions at a low power and low gas flow rate, which should be useful for uranium fundamental characteristic studies and on-site uranium monitoring work. [Copyright &y& Elsevier]