Absolute Line Intensities Research Articles

Atomic data and spectral line intensities for Mg VI

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Mg VI. The configurations used are 2s 22p 3, 2s2p 4, 2p 5, 2s 22p 23s, 2s 22p 23p, and 2s 22p 23d, giving rise to 72 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies, 12, 24, 36, 48, and 60 Ry. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10 8–10 14 cm −3 at an electron temperature of log T e (K) = 5.6, corresponding to maximum abundance of Mg VI. Relative and absolute spectral line intensities are calculated and compared with observations of a solar active region.

12C 16O 2 line intensity FTS measurements with 1% assumed accuracy in the 1.5–1.6 μm spectral range

Using Fourier-transform spectra and a multispectrum fitting procedure, 124 absolute line intensities of 12C 16O 2 are obtained for the cold band 30011–00001 and the hot band 01131–01101 between 6460 and 6950 cm −1. Vibrational transition dipole moments squared and Herman–Wallis coefficients are reported for each band. Cross comparisons made with previous experimental results and with data available in the HITRAN and Carbon Dioxide Spectroscopic Databank (CDSD), bring some confidence on the good level of accuracy of the present results. Motivated by the demanding needs of some atmospheric experiments dedicated to the survey of the carbon cycle, an additional evaluation of potential absolute line intensity measurement limit is also performed on recently published carbon dioxide absolute line intensity independent measurements. These are obtained in two different laboratories on the bands 30013–00001 and 30012–00001 both located in the 1.6 μm spectral window. It is shown that Fourier-transform experimental CO 2 line intensity determination is approaching the challenging required figure of about 0.3% accuracy needed for the survey of the atmospheric carbon cycle.

12C 16O 2 line intensity measurements around 1.6 μm

Using Fourier transform spectra and a multispectrum fitting procedure, 271 absolute line intensities of 12C 16O 2 have been measured around 1.6 μm, for the three cold bands 30014-00001, 30013-00001, and 30012-00001, and for the two hot bands 31113-01101 and 31112-01101, extending from 6035 to 6380 cm −1. Accuracies are on the average 3 and 5% for cold and hot bands, respectively. Vibrational transition dipole moments and Herman–Wallis coefficients are reported for each band. Comparisons are made with previous experimental results and with data available in the HITRAN database and the Carbon Dioxide Spectroscopic Databank (CDSD).

Optical emission spectroscopy of metal-halide lamps: Radially resolved atomic state distribution functions of Dy and Hg

Absolute line intensity measurements are performed on a metal-halide lamp. Several transitions of atomic and ionic Dy and atomic Hg are measured at different radial positions from which we obtain absolute atomic and ionic Dy intensity profiles. From these profiles we construct the radially resolved atomic state distribution function (ASDF) of the atomic and ionic Dy and the atomic Hg. From these ASDFs several quantities are determined as functions of radial position, such as the (excitation) temperature, the ion ratio Hg+∕Dy+, the electron density, the ground state, and the total density of Dy atoms and ions. Moreover, these ASDFs give us insight about the departure from equilibrium. The measurements show a hollow density profile for the atoms and the ionization of atoms in the center. In the outer parts of the lamp molecules dominate.

Atomic data and spectral line intensities for Ar XI

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ar XI. The configurations used are 2s 22p 4, 2s2p 5, 2p 6, 2s 22p 33s, 2s 22p 33p, and 2s 22p 33d giving rise to 86 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies (30, 60, 90, 120, and 150 Ry) in the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10 8–10 14 cm −3 at an electron temperature of log T e (K) = 6.3, corresponding to the maximum abundance of Ar XI. Relative and absolute spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.

Asymmetric charge transfer with hydrogen ions — An important factor in the “hydrogen effect” in glow discharge optical emission spectroscopy

It is now well known that traces of hydrogen or nitrogen in the argon plasma gas in glow discharge optical emission spectrometry (GD-OES) may affect the sputtering rate. More seriously, such traces can also selectively affect the absolute and relative intensities of individual lines, and thereby have a major effect on the accuracy of analytical results. This problem is becoming more severe as the potential of GD-OES as an analytical tool is steadily increasing, and the technique is now used for the analysis of more complex samples. The results presented form part of an extensive study of the effects of hydrogen and nitrogen on the spectra of a number of elements — Fe, Ti, V, Ni, Zn etc. Two systems have been used to record the spectra for the present results — high resolution Fourier transform spectroscopy at Imperial College, London, and the LECO GDS500A, with CCD spectrometer at LECO Instrumente, Plzeň. The two approaches have yielded consistent results. During the analysis of the data for Fe II and Ti II spectra, it has become clear that asymmetric charge transfer involving hydrogen ions (H-ACT) is a very important selective excitation mechanism for spectral lines with a total excitation energy close to 13.6 eV, the ionisation potential of hydrogen. Detailed evidence for this mechanism is presented. The magnitude of the effect varies for different elements and spectral lines but great care must be taken before choosing ionic lines with a total excitation energy of between 12.5–14 eV for analytical use.

Absolute line intensities in methyl bromide: The 7-μm region

This work deals, for the first time, with the modeling of absolute line intensities in the fundamental ν 2 and ν 5 bands of CH 3 79Br and CH 3 81Br at 7 μm. For that, four unapodized absorption spectra of CH 3Br (natural abundance, 99% purity, P × L = 0.082 − 0.165 atm × cm, room temperature) were measured in the range 1260–1560 cm −1, at a resolution of 0.002 cm −1 using a Fourier transform spectrometer Bruker IFS 120 HR. For both isotopomers, 313 line intensities were analyzed within the dyad system required to account properly for the strong Coriolis coupling between ν 2 and ν 5. The intensity fit of experimental data led to the determination of the dipole moment derivatives d 2 = ∂ μ/∂ q 2 and d 5 = ∂ μ/∂ q 5 relative to the ν 2 and ν 5 bands, as well as the first-order Herman–Wallis correction in K to d 5. The observed line intensities are fitted to 3.0% (3.3%) for ν 2 at 1309.9 cm −1 and 2.6% (3.0%) for ν 5 at 1442.9 cm −1, respectively for CH 3 79Br and CH 3 81Br. The values derived for the vibrational band strengths of ν 2 and ν 5 are 55.7(0.6) and 39.2(0.3) cm −2 atm −1 at 296 K, respectively. The corresponding assignments and line positions of the dyad from previous work [F. Kwabia Tchana, I. Kleiner, J. Orphal, N. Lacome, O. Bouba, J. Mol. Spectrosc. 228 (2004) 441] are combined with the present intensity study to provide an improved CH 3Br database for atmospheric applications.

Atomic data and spectral line intensities for Ca XIII

Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ca XIII. The configurations used are 2 s 2 2p 4 , 2s2p 5 , 2p 6 , 2s 2 2p 3 3s, 2s 2 2p 3 3p and 2s 2 2p 3 3d giving rise to 86 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies (40, 80, 120, 160 and 200 Ry) in the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10 8 -10 14 cm -3 at an electron temperature of log T e (K) = 6.5, corresponding to maximum abundance of Ca XIII. Relative and absolute spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.

Absolute line intensities of 13C 16O 2 in the 3090–3920 cm −1 region

Absolute line intensities of 13C 16O 2 were retrieved from high-resolution Fourier transform spectra recorded in the region 3090–3920 cm −1. The uncertainty of the line intensity determination is estimated to be between 3 and 5% for the strong lines. The global fittings of the observed line intensities within the framework of the effective operators approach have been performed, reaching the experimental accuracy. A comparison of newly measured line intensities with those found in the HITRAN database is presented.

Absolute line intensity with FT-ICLAS: 12C 2H 2 near 12 800 cm −1

We have used a Fourier transform intracavity laser absorption spectrometer to measure the absolute intensity of lines in the ν 1 + 3 ν 3 band of 12C 2H 2 at 12675 cm −1. Under optimal conditions the agreement is found to be within 5% of reference values measured by conventional Fourier transform spectroscopy [F. Herregodts et al., Mol. Phys., 101 (2003) 3427]. The absolute intensity of 21 weaker lines not experimentally investigated in the latter work, is listed. Various tests of the instrumental method are presented, also demonstrating its ability to determine pressure self-broadening coefficients.

Absolute line intensities for carbonyl sulfide from 827 to 2939 cm −1

Using a total of 18 unapodized high-resolution (MOPD=300 and 450 cm) Fourier transform absorption spectra of carbonyl sulfide ( P× ℓ=14.3–60,600 Pa×cm, T=296.0 K), we measured 1340 absolute line intensities in 8 bands ( ν 1 + ν 2 1 − ν 2 1 , 2 ν 2 0 , 2 ν 1 , ν 1 + 2 ν 2 0 , 4 ν 2 0 , ν 3 , ν 2 1 + ν 3 − ν 2 1 , ν 1 + ν 3 ) of the main isotopologue, located between 827 and 2939 cm −1. In addition, we measured 307 absolute line intensities in the ν 3 fundamental band of 16O 12C 34S and 16O 13C 32S, observed near 2061.45 and 2009.23 cm −1, respectively. The observed Herman–Wallis dependences are in most cases reproduced by the global model of OCS [E. Rbaihi, A. Belafhal, J. Vander Auwera, S. Naïm, and A. Fayt, J. Mol. Spectrosc., 191:32–44, 1998]. The pressure self-broadening parameter was also measured up to J=83.

Absolute line intensities of 13C 16O 2 in the 4200–8500 cm −1 region

The absolute line intensities of 13C 16O 2 were retrieved from Fourier-transform spectra recorded in the region 4200–8500 cm −1. The accuracy of the line intensity determination is estimated to be 5% or better for most lines and about 10% for weak ones. The vibrational transition dipole moments squared and Herman–Wallis coefficients have been determined. The global fittings of the observed line intensities within the framework of the effective operators approach have been performed. As the result of the fittings, most line intensities are reproduced within the experimental accuracy. The comparison between the new measured data and the HITRAN database are also carried out.

Fourier transform and high sensitivity cw-cavity ringdown absorption spectroscopies of ozone in the 6030–6130 cm −1 region. First observation and analysis of the 3 ν1+3 ν3 and 2 ν2+5 ν3 bands

The absorption spectrum of 16O 3 has been recorded between 6030 and 6130 cm −1 by Fourier Transform Spectroscopy (GSMA, Reims) and cw-cavity ringdown spectroscopy (LSP, Grenoble). The two new bands 3 ν 1+3 ν 3 and 2 ν 2+5 ν 3 centered at 6063.923 and 6124.304 cm −1, respectively are observed and analyzed. Rovibrational transitions with J and K a values up to 40 and 10, respectively, could be assigned. The rovibrational fitting of the observed energy levels shows that some rotational levels of the (303) and (025) bright states are perturbed by interaction with the (232), (510) and (124) dark states. The observed energy levels could be reproduced with a rms deviation of 5×10 −3 cm −1 using a global analysis based on an effective Hamiltonian including the five interacting states. The energy values of the three dark vibrational states provided by the fit are found in good agreement with theoretical predictions. The parameters of the resulting effective Hamiltonian and of the transition moment operator retrieved from the measured absolute line intensities allowed calculating a complete line list of 2035 transitions, available as Supplementary Material. The integrated band strengths are estimated to be 1.22×10 −24 and 3.15×10 −24 cm −1/(mol cm −2) at 296 K for the 3 ν 1+3 ν 3 and 2 ν 2+5 ν 3 bands, respectively. A realistic error for these band strengths is 15% (see text).

Absorption spectra of 12C 16O 2 and 13C 16O 2 near 1.05 μm

The absolute line intensities of the Fermi triad 2003 i–00001 ( i = 1, 2, 3) of 12C 16O 2 and 13C 16O 2 isotopic species of carbon dioxide were retrieved from Fourier-transform spectra recorded at Doppler limited resolution in the region 9200–9700 cm −1. The accuracy of the line intensity determination is estimated to be better than 15% for most lines. The vibrational transition dipole moments squared and Herman–Wallis coefficients have been determined. The global fittings of the observed line intensities within the framework of the effective operators method have been performed. The fitting results reproduce the data within experimental uncertainty.

Atomic data and spectral line intensities for Ca XIV

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ca XIV. The configurations used are 2s 22p 3, 2s2p 4, 2p 5, 2s 22p 23s, 2s 22p 23p, 2s 22p 23d, and 2s2p 33s giving rise to 91 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies: 45, 90, 135, 180, and 225 Ry. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10 8–10 14 cm −3 at an electron temperature of log T e (K) = 6.5, corresponding to a maximum abundance of Ca XIV. Relative and absolute spectral line intensities are calculated and compared with observations of a solar active region and of tokamak plasma.

Phase-shift cavity ring-down spectroscopy to determine absolute line intensities

Cavity ring-down detection techniques can sensitively determine frequency-dependent absorption cross-sections of gasses. However, so-called line-width problems and amplified spontaneous emission of the laser light source lowers the technique’s quantitative accuracy. Using phase-shift cavity ring-down spectroscopy (PSCRD), we measured absolute line intensities of the spin-forbidden transitions in the b 1 Σ g + ( ν ′ = 0 ) ← X 3 Σ g - ( ν ″ = 0 ) band of molecular oxygen. Our results were within 4% of values obtained from the HITRAN database, demonstrating the accuracy of PSCRD, when corrected for amplified spontaneous emission. Its high sensitivity (2 × 10 −8 cm −1), simplicity and high duty cycle make PSCRD a powerful diagnostic technique.

Theoretical rovibrational line intensities in the electronic ground state of ozone

First-principles calculations of absolute line intensities and rovibrational energies of ozone (16O3) are reported using potential energy and electric dipole moment functions calculated by the internally contracted MRCI approach. The rovibrational energies and eigenfunctions (up to about 8500 cm−1 and J = 64) were obtained variationally with an exact Hamiltonian in internal valence coordinates. More than 4.8 × 106 electric dipole transition matrix elements were calculated for the absolute rovibrational line intensities. They are compared with the values of the HITRAN database. The purely rotational absolute line intensities in the (000) state and the rovibrational intensities for the (001)–(000) band agree to within about 0.3 to 1% for the (010)–(000) band to within about 3 to 4%. Excellent agreement with experiment is also achieved for low-lying overtone and combination bands. Inconsistencies are found for the (100)–(000) band overlapping with the antisymmetric stretching fundamental and also for the (002)–(000) antisymmetric stretching overtone. The generated dipole moment function can be used for predicting the absorption intensities in any of the heavier isotopomers, hot bands or the rates of spontaneous emission.

Measurements of the temperature of subsonic CO2 induction plasma flows by analyzing their emission spectra

Results are presented from measurements of the temperature characteristics of subsonic CO{sub 2} plasma flows generated by a 100-kW induction plasmatron at the Institute for Problems of Mechanics, Russian Academy of Sciences. The atomic excitation temperature T{sub a} and the population temperature T{sub e} of the electronic states of C{sub 2} molecules (both averaged over the jet diameter) were measured from the absolute intensities of the atomic spectral lines and the spectrum of C{sub 2} molecules in different generation regimes at gas pressures of 25-140 hPa and anode supply powers of 29-72 kW. The longitudinal and radial profiles of the temperatures were determined for some of these regimes and compared to those obtained from numerical calculations of equilibrium induction plasma flows in the discharge channel. For some generation regimes, the dependences of the averaged (over the line of sight) rotational and vibrational temperatures (T{sub r} and T{sub v} ) on the discharge parameters, as well as the radial profiles of these temperatures, were determined from the best fit of the measured and calculated spectra of C{sub 2} molecules (Swan bands). The self-absorption of molecular emission was observed at sufficiently high temperatures and gas pressures, and its influence on the measuredmore » values of the molecular temperatures T{sub e} , T{sub v} , and T{sub r} was examined.« less

Line intensities of acetylene at [formula omitted

More than 400 absolute line positions and intensities of acetylene have been measured for the two cold bands ν 3 and ν 2 + ( ν 4 + ν 5 ) + 0 , and four strong hot bands occuring in the 3- μ m spectral region, from Fourier-transform spectra. Accuracies are on the average 0.0005 cm - 1 for line positions and 5% for line intensities. Vibrational transition dipole moment values have been deduced, as also empirical Herman–Wallis coefficients, and comparisons have been made with previous results.

Absolute line intensity measurements of hot bands for carbonyl sulfide at 12 μm

Using diode-laser spectroscopy, the intensities of 58 lines of the ν 1+ ν 2 1− ν 2 1 band and 36 lines of the 2 ν 1− ν 1 band of OCS have been measured. The corresponding band strengths S ν 0 and the vibrational transition dipoles μ ν have been derived through least squares fitting of these individual intensities. The band strengths values have been determined with a precision better than 2.5%.