Half-widths Of Spectral Lines Research Articles

Unusually Powerful Flare Phenomenon of the Water Maser in W51 and the Possibility of Detecting Gravitational Radiation from It

Because of detailed monitoring of the 22.2 GHz water maser, carried out from 2021 October to 2023 May, a very powerful flare phenomenon was detected in the galactic object W51 near the radial velocity of 60 km s−1 with the amplitude of 140 kJy. A phenomenon of this magnitude was unprecedented in the entire history of observations of the source. Eleven short flares were recorded. The exponential increase and decrease in the flare flux density while reducing in their spectral line widths indicated that water masers were in an unsaturated state during the flares. All flares were located at the top of the less powerful Flare 0 with the amplitude of 13.5 kJy and the spectral line half-width of 3.0 km s−1. Such a wide line of the water maser, as well as the amplitude, of the flare phenomenon are so far unique discoveries. The water maser of Flare 0 may have been saturated and created a significant input flux density for other flares of this phenomenon. The extremely high density of maser spots in a cluster led to their partial overlap on the observer’s line of sight. This also confirmed the hypothesis about the need for a significant length of the path along which the generation of maser radiation occurs. New parameters of water masers and the most important physical conclusions have been obtained. The possibility of detecting gravitational waves from massive binary stars at the stage of evolution close to merging is considered for the case of W51 Main.

Measurement of Stark Halfwidths of Spectral Lines of Ionized Oxygen and Silicon Emitted from T-tube Plasma

The analysis of experimental Stark halfwidths of spectral lines of singly ionized oxygen and silicon and double ionized silicon is presented in this work. The considered spectral lines were emitted from plasma generated in an electromagnetically driven T-tube, with an electron temperature of 15,000 K and electron density of 1.45 × 1023 m−3. The obtained Stark halfwidths were compared to experimental values given by other authors. In addition, all experimental values were compared to theoretical values. These data are useful for diagnostics of laboratory and astrophysical plasmas as well as verifying theoretical models.

Theoretical Models of Low-Resolution Microwave Rotational Spectra of Ethane- and Propanethiol

Additive modeling of low-resolution microwave spectra of heteroisomeric substituted hydrocarbons produced theoretical spectra of ethanethiol and propanethiol in the range 0–2 THz with maxima at 465 ± 20 and 240 ± 20 GHz. More precise calculations in a narrow frequency band of these ranges used spectral line half-widths of 1.5, 0.8, and 0.5 MHz that modeled conditions in different layers of Earth’s troposphere. The strongest extrema of the low-resolution spectra of the studied molecules were found at 486 ± 5, 446 ± 5, and 436 ± 5 (ethanethiol) and at 257 ± 5, 239 ± 5, and 234 ± 5 GHz (propanethiol). Various aspects of the application of the results were discussed.

Raman Scattering by Crystals of Rare-Earth Hexaborides with Different Isotopes of Boron

Monocrystals of lanthanum hexaboride LaB6 containing both natural boron and its isotopes 10B and 11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.

Рамановское рассеяние кристаллами гексаборидов редких земель с различными изотопами бора

AbstractMonocrystals of lanthanum hexaboride LaB_6 containing both natural boron and its isotopes ^10B and ^11B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.

Spectroscopic nanoporometry of aerogel

The sizes of aerogel nanopores from the measured broadening of rotational-vibrational CO lines caused by collisions with nanopore walls have been determined. It has been shown that the sizes of nanopores with a diameter of 15–25 nm can be reliably assessed from the half-widths of spectral lines measured on a high-resolution Fourier spectrometer and agree well with the experimental data found from the low-temperature adsorption of nitrogen.

Fourier spectroscopy of water vapor in the volume of aerogel nanopores. Part 1. Measurements and calculations

Broadening and shifting of absorption lines of water vapor confined inside aerogel nanopores have been studied with the help of a IFS 125 HR Fourier spectrometer in the region 5000–5600 cm−1. It is shown that strong spatial limitation of molecular movement results in significant broadening and shifting of spectral lines. A semiempirical model for description of the form of absorption line contours for H2O molecules confined inside aerogel nanopores, taking account of the dependence of spectral line half-width on rotational quantum numbers, is presented for the first time. Values of spectral line half-widths found experimentally and theoretically are in good agreement.

Theory of relaxation parameters of the spectrum shape in the impact approximation−II: Simplifications, application for qQ(J,K) doublets in the v1 band of NH3 self-broadening

In the first part of this paper the general theory of relaxation parameters of the spectrum shape in the impact approximation was presented. Here we describe some simplifications, discuss the isolated line approximation and compare our results with the other methods of a spectral line half-width and center shift calculation. As an example, illustrative calculations of the qQ(J,K) doublets in the v1 band of NH3 self-broadening have been performed and the results are compared with the experiment.

Luminescence spectra fine structure for uranyl sulfate and oxalate crystals

Quasi-line low-temperature (T = 77 and 4.2 K) luminescence spectra of uranyl sulfates and oxalates have been recorded and analyzed. It has been shown that the spectral structure is determined by the manifestation of the internal and external vibrations of both the uranyl ion and molecular groups (SO 4 ) 2- and (C 2 O 4 ) 2- bonded to the uranyl ion. The spectral line half-width is of the order of ≈5-7 cm -1 ; the line shape, close to Lorentzian. The fluorescence spectra may be complicated by structural defects in the crystals.

A method for estimating the error in determining the position of XPS sectral lines from experimental data

A method is proposed for estimating the errors in determining the position of spectral lines, which takes into account possible errors of the measuring instrument and methods of mathematical treatment of spectra, as well as their dependence on the half-width of spectral lines, spacing between them, and the background noise height.

Modification of the Robert–Bonamy formalism in calculating Lorentzian half-widths and shifts

We have found an invalid assumption in the Robert–Bonamy formalism that has been widely used for calculating Lorentzian spectral line half-widths and shifts for decades. The problem results in their derivation where they assumed the cumulant expansion can be used to evaluate the Liouville matrix element 〈 〈 j 2 i 2 | S ^ | j 2 i 2 〉 〉 . At first sight, their assumption appears to be correct because this matrix element is diagonal in the Liouville space and as a result, it looks like that a basic requirement in applying the cumulant expansion is satisfied. However, by decomposing it into two Hilbert matrix elements associated with S I and S F ( S ^ = S I S F * ) , respectively, we have found that neither of these is diagonal in Hilbert space. Therefore, their assumption is not valid and their expressions for the half-widths and shifts are incorrect. We have found by choosing an average over the internal degrees of the bath molecule as the average in the cumulant expansion, one is able to apply this expansion properly and obtain the correct expressions. Numerical calculations show new half-width and shift values differ from previous ones, and the stronger the interaction between two molecules is, the larger these differences are.

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

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

Measurements of line intensities and half-widths in the 10-μm bands of [formula omitted

We present measurements of the absolute intensities and collision-broadened half-widths of spectral lines in the 10 μm bands of 14 NH 3 . H 2-broadened, N 2-broadened, and O 2-broadened half-widths of lines aP(6,5)– aR(8,8) have been measured at 200, 255, and 296 K . Air-broadened and self-broadened half-widths are presented at 296 K . The variation of linewidths with the temperature and with the rotational quantum numbers J and K is examined. A polynomial function of m and K which fits the observed linewidths accurately is presented.

Measurements of line intensities and line widths in the ν3-fundamental band of nitrous oxide at atmospheric temperatures

We present measurements of the absolute intensities, N 2-, O 2-, and air-broadened half-widths of spectral lines in the 4.5 μm ( ν 3-fundamental) band of 14 N 2 16 O at 216, 250 and 296 K . These data were obtained using a high-resolution ( 0.002 cm −1) Fourier-transform spectrometer. The variation of the line widths with temperature and the rotational quantum number m (| m| is J in the P-branch and J+1 in the R-branch, with J being the rotational quantum number of a linear molecule) is examined. Simple empirical polynomial (quartic) fits of the measured half-widths are presented. A new improved method of extrapolation of line-width data to higher values of m has also been devised.

Normal vibrational modes in benzil crystals

A group-theoretical analysis of the vibrational spectrum of benzil crystals was carried out. The selection rules and normal coordinates were found. Raman scattering spectra of benzil single crystals were studied in polarized light within a broad temperature range from 100 K to the melting point (T m=96°C). The experimental data were found to correlate with theory. The temperature dependences of the spectral-line half-widths were used to separate the observed vibrations into translational and librational modes, and the correspondence between the experimentally observed vibrations and their normal coordinates was established in some cases.

Plasma parameters of an argon DC arc with graphite electrodes

Plasma temperature and electron density have been measured by optical emission spectroscopy in a transferred direct current arc with graphite electrodes. The measurements were realized for the arc running in a 1.7 cm3 s-1 argon flow at atmospheric pressure, a current of 200 A, a voltage of 48±2 V and with a distance of 85 mm between the electrodes. Specially designed electrodes were developed to minimize displacements of the arc because of movements of the electrode spots. In this way, the measurement errors have been greatly diminished. The measurements were made supposing an optically thin collisionally dominated plasma of axial symmetry. Density distributions of excited argon atoms and ions on their energy levels were determined to evaluate plasma temperature. The half-widths of spectral lines were used to reach the electron density in the plasma. Spatial distributions of the measured parameters are presented for the arc positive column and near the electrodes. Maximum values of 1.5 × 1017 cm-3 and 13 500 K were found close to the cathode for the electron density and temperature, respectively. The data and possible reasons for some of the variation found in the observed results are discussed.

Simplified Method for the Rotational Temperature Determination of Carbon Monoxide from Absorption Spectra Measured at High Resolution

Abstract A fast and convenient method for determining the temperature of hot gas from their Fourier transform infrared absorption spectra was given on the bases of band fitting method. According to the half-width of spectral lines measured at different temperature, we studied the effect of the index of a particular line, m, on the half-width of spectral lines. Almost 27 rotation-vibration lines in the P- and/or R-branches of foundamental band of CO were used in this procedure. Quantitative evaluations of the gas temperature indicate that the temperature can be measured with an accuracy better than 2.7%. In addition, this formular is applied to other spectra reported in literature. Temperatures calculated by our method also have good results.

Determination of half-width of spectral lines of radiation of an inhomogeneous plasma

Determination of half-width of spectral lines of radiation of an inhomogeneous plasma

Intensities, half-widths and shapes of spectral lines in the fundamental band of CO at low temperatures

Intensities and half-widths of spectral lines in the R-branch of the C 12O 16 fundamental band have been measured at 200, 150, 99, and 81 K. The broadeners used were CO, N 2, O 2, and CO 2. The validity of some representative theories relevant to these line parameters have been examined in the light of the present results. We also discuss the shape of CO lines at low temperatures.

Measurements of intensities and self- and foreign-gas-broadened half-widths of spectral lines in the CO fundamental band

Accurate measurements of the intensities and the self-, nitrogen-, oxygen-, and carbon-dioxide-broadened half-widths of spectral lines in the carbon monoxide fundamental band have been made at 300 K. Data reduction was made by using an iterative procedure to correct for overlapping with neighboring lines and the non-linearity of the curve-of-growth. Results are derived by using the Benedict line profiles.