High-resolution Fourier-transform Spectra Research Articles

New Ritz Wavelengths and Transition Probabilities of Parity-forbidden [Mn II] Lines of Astrophysical Interest.

We report a comprehensive list of accurate Ritz wavelengths and calculated transition probabilities for parity-forbidden [Mn II] lines. Ritz wavelengths have been derived from experimentally established energy level values resulting from an extensive analysis of a high-resolution Fourier-transform emission spectrum of singly ionized manganese. Our analysis includes transitions between all known metastable and other long-lived levels of Mn II giving a total of 1130 [Mn II] Ritz wavelengths. Our entire list of derived Ritz wavelengths for [Mn II] lines ranges between 237 nm and 170 μm (42,125-58 cm-1). The accurate Ritz wavelengths and calculated transition probabilities for forbidden lines in this paper are useful in the study and diagnostics of nebulae and other low-density astrophysical plasmas.

Finding of previously unknown energy levels using Fourier-transform and laser spectroscopy

In this paper several possibilities of how to find previously unknown energy levels from high-resolution Fourier-transform or laser-generated spectra are discussed. As examples we use levels of neutral Ta, Pr and La. The following methods are used: analysis of Fourier-transform emission spectra, laser-excitation of unclassified spectral lines, analysis of the hyperfine structure of unclassified lines. The discovery of two new La I energy levels is reported.

Far-infrared 14NH3 line positions and intensities measured with a FT-IR and AILES beamline, Synchrotron SOLEIL

Extensive measurements of line positions and intensities are reported for the inversion-rotation and rovibrational transitions of 14NH3 in the 50–660cm−1 region. This study analyzes high-resolution (0.00167cm−1, unapodized) Fourier-transform spectra of high purity (99.5%) normal ammonia sample obtained using the AILES beamline of Synchrotron SOLEIL. The experimental conditions are designed to study transitions with intensities weaker than 1×10−22cm−1/(moleculecm−2) at room temperature. Line positions and intensities of more than 2830 transitions of 14NH3 are measured and compiled after proper quality control; the features from minor isotopologues (15NH3 and NH2D) and H2O are identified and excluded. Based on the predictions of recent work from the empirical Hamiltonian modeling, systematic quantum assignments are made for 2047 transitions from eight bands including four inversion-rotation (gs, v2, 2v2, and v4) and four ro-vibrational bands (v2–gs, 2v2–v2, v4–v2, and 2v2–v4), as well as covering their ΔK=3 forbidden transitions. The measured line positions for the assigned transitions are in an excellent agreement (typically better than 0.001cm−1) with the predictions in a wide range of J and K for all the eight bands. The comparison with the HITRAN 2012 database is also satisfactory, although systematic offsets are seen for transitions with high J and K and those from weak bands. Also we note that out of the eight bands, the 2v2–v4 has not been listed in the HITRAN 2012 database. Differences of 20% are seen between our measured and calculated intensities depending on the bands. For line positions, greater differences are found for some NH3 bands in HITRAN 2012 than recent predictions. Measurements of the individual line positions and intensities are presented for the eight bands, and the final spectroscopic line positions and intensities are compiled as an electronic supplement.

Lowest vibrational states of acrylonitrile from microwave and synchrotron radiation spectra

The high resolution Fourier-transform spectrum of acrylonitrile covering the 40–700cm−1 spectral region was recorded at the AILES infrared beamline of the SOLEIL synchrotron. The spectrum allowed assignment of vibration–rotation transitions in four different fundamental bands, five hot bands, one overtone band, as well as of some pure rotational transitions. The new infrared data and previous measurements made with microwave techniques have been combined into a single global fit encompassing over 31000 measured transitions. Precise vibrational term values have been determined for the eight lowest excited vibrational states, including ν11=228.299930(4), ν15=332.678207(4), ν10=560.716701(5), and ν14=681.793862(13)cm−1. The new values are compared with those obtained previously entirely on the basis of rotational perturbations. Several anharmonicity coefficients are determined and compared with abinitio anharmonic force field calculations. The assignment of the ν10 mode is also clarified.

N2-broadening coefficients of methyl chloride at room temperature

Methyl chloride is of interest for atmospheric applications, since this molecule is directly involved in the catalytic destruction of ozone in the lower stratosphere. In a previous work [Bray et al. JQSRT 2011;112:2446], lines positions and intensities of self-perturbed 12CH335Cl and 12CH337Cl have been studied into details for the 3.4μm spectral region. The present work is focused on measurement and calculation of N2-broadening coefficients of the 12CH335Cl and 12CH337Cl isotopologues. High-resolution Fourier Transform spectra of CH3Cl–N2 mixtures at room-temperature have been recorded between 2800 and 3200cm−1 at LADIR (using a classical source) and between 47 and 59cm−1 at SOLEIL (using the synchrotron source on the AILES beamline). 612 mid-infrared transitions of the ν1 band and 86 far-infrared transitions of the pure rotational band have been analyzed using a multispectrum fitting procedure. Average accuracy on the deduced N2-broadening coefficients has been estimated to 5% and 10% in the mid- and far-infrared spectral regions, respectively. The J- and K-rotational dependences of these coefficients have been observed in the mid-infrared region and then a simulation has been performed using an empirical model for 0≤J≤50, K≤9. The 12CH335Cl–N2 line widths for 0≤J≤50 and K≤10 of the ν1 band and for 55≤J≤67 and K≤15 of the pure rotational band have been computed using a semi-classical approach involving exact trajectories and a real symmetric-top geometry of the active molecule. Finally, a global comparison with the experimental and theoretical data existing in the literature has been performed. Similar J- and K-rotational dependences have been appeared while no clear evidence for any vibrational or isotopic dependences have been pointed out.

(000) and (010) energy levels of the HD18O and molecules from analysis of their ν2 bands

Abstract High-resolution Fourier-transform spectra of water samples enriched by deuterium and oxygen-18 at room temperature are analyzed in the range 969–2148 cm−1. Line positions of about 2470 transitions up to Jmax = 22 and Ka max = 12 of the ν2 bands of the HD18O and D 2 18 O molecules are reported. This has allowed the determination of extended sets of rotational energies of the (0 0 0) and (0 1 0) vibrational states for both molecules. The generation function model of an effective rotational Hamiltonian was used in the data reduction to account for the strong centrifugal distortion of the rotational levels. Values of effective Hamiltonian parameters have been determined. The RMS standard deviations of the least-squares fits of the energy levels were 2.4 × 10−4 cm−1 for 293 energy levels of the ground state and 3.2 × 10−4 cm−1 for 281 energy levels of the (010) state of D 2 18 O , and 2.6 × 10−4 cm−1 for 227 energy levels of the ground state and 4.2 × 10−4 cm−1 for 246 energy levels of the (0 1 0) state of HD18O. Comparisons of obtained data with the theoretical predictions as well as with other observations are presented.

On the Rotational Temperature of AlH in Sunspots

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 A), Tech. Rep. 00-001, National Solar Observatory, Tucson, AZ, 2000), 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 (2000). 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.

Fourier transform absorption spectrum of [formula omitted] in 7360–8440 cm −1 spectral region

The high-resolution Fourier-transform spectrum of the D 2 16O molecule is recorded and analyzed in the region near 1.27 μ m (7360–8440 cm −1) where the bands of the V=3 ( V= v 1+ v 2/2+ v 3) polyad are located. A total of 2772 transitions have been assigned based on recent variational calculation of Shirin et al. [JQSRT 2008;109:549–58]. A set of 1094 energy levels (564 of which are new) is determined for nine vibrational states including those of newly reported (1 0 2) and (2 2 0) states. Calculations using an effective Hamiltonian are performed to establish reasonable ro-vibrational labeling of the observed energy levels. The latest variational calculation are found to agree well with the experiment for line positions (within 0.026 cm −1 on average); however, the calculated intensities for transitions to upper energy levels which are in close resonance with other states can be distorted.

On the search for BF, BH and BS molecular lines in sunspot spectra

A search has been carried out for the presence of rotational lines of boron containing diatomic molecules BF, BH and BS in the high resolution Fourier Transform Spectra of sunspots observed at the National Solar Observatory in Kitt Peak. The spectra were examined for a large number of rotational lines due to nine bands of BF, ten bands of BH and eight bands of BS in the range 9600–25,500 cm −1. The presence of the lines due to six bands of BF and five bands of BS is confirmed. However, the presence of BH is found to be questionable. Equivalent widths have been measured for well resolved lines of BF and BS and effective rotational temperatures have been estimated.

High-resolution spectroscopy of the triple-substituted isotopologue of water molecule D_{\\bf 2}^{\\bf 18}O: the first triad

The high-resolution Fourier-transform absorption spectrum of the triple-substituted isotopologue of the water molecule, DO is measured in the 1700–9000 cm−1 region. The transitions of the ν1, 2ν2 and ν3 bands are assigned with the help of the high accuracy variational calculations based on an empirical mass-dependent Partridge–Schwenke potential energy surface. The fittings based on an effective Hamiltonian model are also utilized to confirm the assignments. A set of 816 precise ro-vibrational energy levels for the first triad of interacting vibrational states: (0 0 1), (1 0 0) and (0 2 0) is retrieved. With the upper state combination differences, the ground state energy levels are extended to J max = 23 and . These levels can be used to check the quality of the recently available high accuracy ab initio potential energy surface of the water molecule.

Rotational and vibrational temperatures of electronically excited BiN radicals in a chemiluminescent flame

Rotational and vibrational temperatures of electronically excited BiN radicals in a low-pressure Bi x +N/N 2*/N 2+Ar chemiluminescent flame have been deduced from high-resolution Fourier-transform emission spectra. Bands of three electronic transitions, a 3Σ +(a 11)→X 1Σ +(X0 +), b 5Σ +(b 10 +)→X 1Σ +(X0 +), and b 5Σ +(b 10 +)→a 3Σ +(a 11), were analysed to determine the optical temperatures in the a 3Σ +(a 11) and b 5Σ +(b 10 +) states. The rotational temperatures characterising the rotational populations in the a 11, v=0 and 1 states were determined from the a 1→X, 0–2, 0–3, 0–4, 1–1, and 1–2 bands. The b 1→X, 0–8 and 0–11 bands, and the b 1→a 1, 0–0 bands served to determine the rotational temperature of the radicals in the b 10 +, v=0 state. The temperatures derived from the various bands and transitions were well consistent and the mean rotational temperature was determined to be 353±18 K, which is close to the translational temperature of the gas. Vibrational temperatures of the radicals in the a 11 and b 10 + states were derived from band intensities of the a 1→X and from the b 1→X as well as b 1→a 1 systems, respectively. The Franck–Condon factors needed were calculated with RKR potentials deduced from literature values of the rotational and vibrational constants in the three states involved. The a 11 vibrational temperature (336±21 K) was close to the rotational temperature, while the b 10 + vibrational temperature (438±36 K) differed, likely due to the previously observed perturbation of the b 10 + state.

Spectroscopic lineshape study of the self-perturbed oxygen A-band

This paper reports accurate line positions, intensities, self-broadening, -shift and -line mixing coefficients for 56 rotational transitions from multispectrum fits of low noise, high-resolution Fourier-transform spectra. The measured line intensities are within the statistical spread of the previous measurements available in the literature—thus contributing to the efforts to measure the oxygen A-band intensities with an accuracy better than 1%. We determined the integrated band strength and Einstein A coefficient. Using our spectrum calibration method we could clearly show for the first time that there is a meaningful statistical discrepancy in the frequency standards used in spectroscopic studies for the oxygen A-band. We were able to explain how this discrepancy leads to two different sets of shifts reported in the literature and demonstrate the need for precise frequency-type transition wavenumber measurements of the oxygen A-band transitions. We observed deviations from the conventional Voigt profile due to speed-dependent broadening and line mixing effects. Dicke narrowing was observed on a selected group of spectra recorded at pressures between 98 and 337 Torr. The Dicke narrowed lineshapes were best modeled using a Galatry profile implemented using a fixed value for the velocity-changing collision rate. The weak line mixing coefficients were determined from fits using the speed-dependent models. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the self-broadening and self-line mixing coefficients.

New high-resolution analysis of the ν1 + 3 ν3 band of nitrogen dioxide in the near infrared spectral region

The high-resolution Fourier-transform absorption spectrum of the 14N 16O 2 molecule was recorded in the near infrared 5200–6005 cm −1 spectral range. Starting from the results of a previous study [R.E. Blank, M.D. Olman, C.D. Hause, J. Mol. Spectrosc. 33 (1970) 109–118] a new analysis of the ν 1 + 3 ν 3 band located at 5984.705 cm −1 has been performed. The new assignments involve energy levels of the (1 0 3) vibrational state with rotational quantum numbers up to K a = 8 and N = 47. The spin–rotation energy levels were satisfactorily reproduced within their experimental uncertainty using a theoretical model which takes explicitly into account the Coriolis interactions between the spin-rotational levels of the (1 0 3) vibrational state and those of (1 2 2) and of (0 8 0), the anharmonic interactions between the (1 2 2) and (0 8 0) vibrational states together with the electron spin–rotation resonances within the (1 0 3), (1 2 2) and (0 8 0) vibrational states. As a consequence, precise vibrational energies, rotational, spin-rotational, and coupling constants were obtained for the triad {(1 2 2), (0 8 0), (1 0 3)} of interacting states of 14N 16O 2. Using these parameters a comprehensive list of line positions and of reliable line intensities was generated for the ν 1 + 3 ν 3 band of NO 2.

The 14–22 μm absorption spectrum of nitrous acid studied by high-resolution Fourier-transform spectroscopy: New analysis of the ν5 and ν6 interacting bands of trans-HONO and first analysis of the ν6 band of cis-HONO

High-resolution Fourier-transform absorption spectra of nitrous acid (HONO) were recorded in the 400–700 cm −1 spectral region. For the trans-HONO isomer a very extensive analysis of the ν 5 (ONO bend) and ν 6 (torsion) interacting fundamental bands of trans-HONO located near 595.620 and 543.879 cm −1, respectively, was performed starting from the results of a previous study [C.M. Deeley, I.M. Mills, L.O. Halonen, J. Kauppinen, Can. J. Phys. 63 (1985) 962–965]. In addition, for the less abundant cis-HONO isomer, the first high-resolution study of the ν 6 band located at 639.7432 cm −1 was achieved, the ν 5 band is presumed to be located near 609.2 cm −1. For both isomers the strong A-type and B-type Coriolis interactions linking the {5 1, 6 1} interacting energy levels were accounted for during the energy level calculations. Finally, using these results a list of positions and of realistic relative line intensities has been generated for both isomers, and a comparison with some ab initio predictions was performed.

Global fit of the high-resolution infrared spectrum of D 2S

High-resolution Fourier-transform spectra of the D 2S molecule in the regions of polyads of interacting vibrational states v = 3/2, 2, 5/2, 3 and 7/2 ( v = v 1 + v 2/2 + v 3) were recorded for the first time with a Bruker IFS 120 Fourier-transform interferometer and analysed. A global fit of all currently available rotation–vibration energies has been made for 22 vibrational states of the D 2S molecule. The resulting set of 231 parameters reproduces all the initial experimental data (about 3670 vibration–rotation energies which correspond to more than 9700 ro-vibrational transitions with J max = 25) with accuracies close to the experimental uncertainties.

Self-broadened 12C16O line shapes in the v=2←0 band

Precise intensities, self-broadenings and shifts have been obtained for the 12C16O v=2←0 band from simultaneous fits of low-noise, high-resolution Fourier-transform spectra at pressures from 27 to 80kPa (200–600 Torr). Observed line shapes exhibit deviations on the order of 1% from the conventional Voigt profile, primarily due to speed-dependent broadening and secondarily to line mixing. Dicke narrowing is reduced by over an order-of-magnitude from the diffusion value, presumably because of correlations between velocity- and phase-changing collisions.

High-Resolution Fourier Transform Spectrum of the D2O Molecule in the Region of the Second Triad of Interacting Vibrational States

The high-resolution Fourier transform spectrum of the D2O molecule was recorded in the 3200–4200 cm−1 region, where the bands of the second triad of interacting vibrational states are located. As a result of the theoretical analysis, both the rotational–vibrational structure of the (011) vibrational state was improved, and the rotational energies of the (110) and (030) vibrational states were determined for the first time up to rotational quantum numbers Jmax. = 15 and 14, respectively.

Analysis of the Lowest 4f-5g Supermultiplet of CoII

The high resolution Fourier-transform emission spectrum from acobalt-neon hollow cathode lamp has been studied in the region9753–9997 Å (10000–10250 cm-1). Of the 54levels of the Co II 3d7(4F)5g subconfiguration,51 are found by means of 144 newly identified transitions to thelevels of the 3d7(4F)4f subconfiguration. Theselines account for the majority of previously unclassified transitionsin this spectral region. The accuracy of the energy levels is a few mK(1mK = 0.001 cm-1). JK coupling is used to representthe 4f and 5g levels and the suitability of this is shown by applyingthe quadrupolic approximation. A classified linelist of the observed4f–5g transitions is given with wavenumbers accurate toapproximately 0.003 cm-1 for strong lines, observedintensities, and calculated oscillator strengths.

High Resolution FTIR Study of the ν5Bands of HSiD3and H120SnD3

High resolution Fourier Transform spectra of HSiD3and monoisotopic H120SnD3have been recorded in the region of the ν5fundamental at 850.68 and 646.90 cm−1with a resolution of 3.3 and 2.8 × 10−3cm−1, respectively. About 2000 rovibrational transitions of each species have been assigned and fitted to two different reductions of the effective Hamiltonian, with σ(Fit) = 1.2 × 10−4(HSiD3) and 1.4 × 10−4cm−1(H120SnD3). The two sets of parameters were shown to be equivalent, and relations between parameters belonging to different reductions are perfectly fulfilled. Furthermore the ground state constantsC0andDK0have been determined for the first time. For consistency the previously measured data belonging to the ν5band of H70GeD3have been refitted, σ(Fit) = 1.6 × 10−4cm−1, on the basis of improved ground state parameters including theh′3term accounting for the splitting of theK= 3 level.

Analysis of 4d–4f Transitions in Co II

The high resolution Fourier-transform emission spectrum from acobalt-neon hollow cathode lamp has been studied in the region4682–6135Å (16300–21360cm-1). Of the 48levels of the Co II 3d7(4F)4f sub-configuration,46 are found by means of 329 newly identified transitions to thelevels of the 3d7(4F)4d subconfiguration. Theselines account for the majority of previously unclassified transitionsin this spectral region. Revised values of 33 levels of the3d7(4F)4d subconfiguration are given and thefive missing levels are found. The accuracy of the energy levels is afew mK (1mK = 0.001cm-1). JK coupling is used torepresent the 4f levels and the suitability of this is shown byapplying the quadrupolic approximation. A classified linelist of theobserved 4d–4f transitions is given with wavenumbers, accurateto 0.001cm-1 for strong lines, and the observedintensities.