We present the first investigation of the ν
8
band (C-C symmetric stretch at 870.3137 cm
−1
), together with an extended analysis of the neighbouring ν
21
band (CH
3
rock at 921.3756 cm
−1
) of ...propane (C
3
H
8
). Our previous investigation of the ν
21
A-type band A.Perrin, F. Kwabia-Tchana, J.M.Flaud, L.Manceron, P.Groner, W.J.Lafferty. J. Mol. Spectrosc. 315, 55 (2015)
r
evealed that the rotational energy levels of 21
1
are split because of interactions with the internal rotations of the methyl groups, leading to the identification of AA, EE, AE and EA torsional components. In this work, a similar behaviour was observed for the B-type ν
8
band and the analysis of the ν
21
band was greatly extended. One of the results of the present study is to show that these torsional splittings are due to the existence of anharmonic and Coriolis resonances, coupling the 21
1
and 8
1
rotational levels to nearby highly excited levels of the two internal rotations of the methyl groups. Accordingly, an effective 'vibration - torsion- rotation' Hamiltonian model was built in the G
36
symmetry group which accounts for both types of resonances. In parallel, a code computing the line intensities was developed to allow unambiguous torsional component assignments. The line assignments were performed using a high resolution (0.0015 cm
−1
) infrared spectrum of propane, recorded with synchrotron radiation at the SOLEIL French light source facility coupled to a Bruker IFS-125 Fourier transform spectrometer. Finally, a linelist of positions and intensities which can be used for the detection of propane in the Earth and outer planets atmospheres was produced.
The far infrared absorption spectrum of HOBr has been measured at high resolution between 100 and 400
cm
−1 using high-resolution Fourier transform spectroscopy. It was possible to identify not only ...1403 pure rotation lines within the vibrational ground state involving levels with rather high
K
a quantum numbers (up to
K
a=9) but also 457 pure rotation lines within the first excited vibrational state 3
1 up to
K
a=7. The ground state lines, combined with 32 microwave transitions available in the literature, were used for a new determination of the rotational constants up to higher orders for both isotopomers HO
79Br and HO
81Br, by least squares fitting of the observed line positions using a Watson-type Hamiltonian for the calculation of rotational energy levels. In the same way the 3
1 rotational lines were fitted together with the few existing microwave transitions and the energy levels derived from the study of the ν
3 band (
J. Orphal, Q. Kou, F. Kwabia Tchana, O. Pirali, and J.-M. Flaud, J. Mol. Spectrosc. 221 (2003), 239–243) leading to an improved set of Hamiltonian constants. Finally relative line intensities were measured and used for the determination of rotational corrections to the
b-component of the permanent dipole moment.
•First investigation of the ν6 band of 35ClNO2.•Fourier transform spectroscopy.•SOLEIL synchrotron.•Unusual structure for a B-type band.
The first investigation of the ν6 band of the 35ClNO2 isotopic ...species of nitryl chloride, located at 410.11824 (± 0.00007) cm−1 has been performed using a high resolution (0.00102 cm−1) Fourier transform spectrum recorded at the SOLEIL synchrotron source. This B-type band is rather weak but a long optical path was used and, during the spectrum recording, the nitryl chloride sample was kept at low temperature (221 K) in the optical cell. In this way, the rather strong ν2–ν3 difference band located at 422.6 cm−1, observed at 296 K during a previous investigation of the far infrared region Orphal J, Morillon-Chapey M, Klee S, Mellau GC, Winnewisser M. J Mol Spectrosc 1998;190:101–6, and interfering with observation, could be strongly reduced. This first assignment of the ν6 band of 35ClNO2 was pursued up to high J and Ka quantum number values, J = 79 and Ka = 37. The ν6 band (expected to be of B-type) has a clearly unusual line intensity pattern, since the P branch is about twice as strong as the R-branch. Since the (weak) ν6 band is located close by to the strong A-type ν3 band located at 370 cm−1 Anantharajah A, Kwabia Tchana F, Manceron L, Orphal J, Flaud JM. J Quant Spectrosc Radiat Transf 2020; 253:107,078, one could reasonably expect that the ν6 band borrows part of its intensity through the existence of a C-type Coriolis resonance that couples together the 61 ⇔ 31 interacting energy levels. However, during the 61 energy level computation, we could not evidence such resonance, and only a classical Watson's type A-type reduced rotational Hamiltonian, involving a single upper state, was used for this calculation.
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Using high-resolution Fourier transform spectra of propane recorded in the 13.4 µm (resolution 0.002 cm
−1
) and in the 27.4 µm (resolution 0.0011 cm
−1
) spectral regions, it was possible to perform ...a thorough assignment of both the ν
26
band at 745 cm
−1
and the 2ν
9
-ν
9
band at about 370 cm
−1
. This simultaneous assignment was necessary since the 26
1
and 9
2
rotational levels interact strongly through an A-type Coriolis interaction. The experimental upper-state rotational levels were fit using a Hamiltonian matrix which takes into account explicitly this strong A-type Coriolis interaction. With this model the experimental energy levels were fit to within their experimental uncertainties and accurate band centres, rotational, centrifugal distortion and coupling constants were determined. The following band centres were derived: ν
o
(ν
26
) = 748.530882(80) cm
−1
and ν
o
(2ν
9
) = 740.29213(10) cm
−1
. Finally, it is shown how the use of these new spectral parameters greatly improves the accuracy of modelling of Titan's infrared spectrum at 13.4 µm, relative to the currently available GEISA atlas for the same band.
We present the first investigation of the ν8 band (C-C symmetric stretch at 870.3137 cm-1), together with an extended analysis of the neighbouring ν21 band (CH3 rock at 921.3756 cm-1) of propane ...(C3H8). Our previous investigation of the ν21 A-type band A.Perrin, F. Kwabia-Tchana, J.M.Flaud, L.Manceron, P.Groner, W.J.Lafferty. J. Mol. Spectrosc. 315, 55 (2015) r evealed that the rotational energy levels of 211 are split because of interactions with the internal rotations of the methyl groups, leading to the identification of AA, EE, AE and EA torsional components. In this work, a similar behaviour was observed for the B-type ν8 band and the analysis of the ν21 band was greatly extended. One of the results of the present study is to show that these torsional splittings are due to the existence of anharmonic and Coriolis resonances, coupling the 211 and 81 rotational levels to nearby highly excited levels of the two internal rotations of the methyl groups. Accordingly, an effective 'vibration - torsion- rotation' Hamiltonian model was built in the G36 symmetry group which accounts for both types of resonances. In parallel, a code computing the line intensities was developed to allow unambiguous torsional component assignments. The line assignments were performed using a high resolution (0.0015 cm-1) infrared spectrum of propane, recorded with synchrotron radiation at the SOLEIL French light source facility coupled to a Bruker IFS-125 Fourier transform spectrometer. Finally, a linelist of positions and intensities which can be used for the detection of propane in the Earth and outer planets atmospheres was produced.
Using Fourier transform spectrometer, He-broadening coefficients have been measured for the first time in the P and R branches of the 2ν1 parallel band of carbonyl sulfide (OCS). The measurements ...have been performed at room temperature for rotational quantum number up to J = 70. A total of 131 lines were measured using a nonlinear least squares multi-pressure spectrum fitting procedure. Since the measurements have been performed using different values of OCS pressures, we have also retrieved line intensities of the ro-vibrational lines of the same branches. The fits were performed using the Voigt profile which leads to a precise determination of these spectroscopic parameters.
From line intensities, we have determined vibrational transition moment, band intensity as well as Herman-Wallis parameters for the 2ν1 band. The results have been discussed as a function of the rotational quantum number and compared to previous data.
The line-mixing effect on broadening coefficients was also analyzed showing a negligible influence.
•He-broadening have been measured for the first time for 131 lines in the 2ν1 of OCS.•The results have been discussed as a function of J and K and branch.•Line intensities, vibrational transition moment, band intensity, and Herman-Wallis parameters have been determined.•The line-mixing effect on broadening coefficients was analyzed.
A Fourier transform spectrum of phosgene (Cl2CO) has been recorded in the 17.3-μm spectral region at a temperature of 180 K and at a resolution of 0.00102 cm-1 using a Bruker IFS125HR spectrometer ...coupled to synchrotron radiation, leading to the observation of the ν2 and ν4 vibrational bands of the two isotopologues 35Cl2CO and 35Cl37ClCO. The corresponding upper-state ro-vibrational levels were fit using a Hamiltonian model accounting for the A-type Coriolis interaction linking the rotational levels of the 21 and 41 vibrational states. In this way, it was possible to reproduce the upper-state ro-vibrational levels to within the experimental uncertainty, i.e. ∼0.30 × 10-3 cm-1. Very accurate rotational and centrifugal distortion and interaction constants were derived from the fit, together with the following band centres: ν0(ν2, 35Cl2CO) = 572.526299(30) cm-1, ν0(ν4, 35Cl2CO) = 582.089026(30) cm-1, ν0(ν2, 35Cl37ClCO) = 568.951791(35) cm-1 and ν0(ν4, 35Cl37ClCO) = 581.758279(35) cm-1.
•Fourier transform spectra of the ν6 band of methyl iodide (CH3I).•Measured of oxygen broadening and shift coefficients in the ν6 band of CH3I.•Modeling of the J and K dependences of the ...O2-broadening coefficients.•Generation of CH3I-air broadening coefficients.
In this study we report the high-resolution measurements of oxygen pressure- broadening and pressure-induced shift coefficients for rovibrational transitions in the ν6 band of methyl iodide (12CH3I), centered at 892.918 cm–1. The results were obtained by analyzing fourteen high-resolution room temperature laboratory absorption spectra with a mono-spectrum non-linear least squares fitting of Voigt profiles. The data were recorded with the Bruker IF125HR Fourier transform spectrometer located at the LISA facility in Créteil, using a White type cell with a path length of 564.9 cm and total pressures up to 295 hPa. The measured oxygen-broadening coefficients range from 0.0648 to 0.1207 cm–1atm–1 at 295 K. The measured shift coefficients were all negative and varied between −0.00044 and −0.04984 cm–1atm–1. The average accuracy on the measured O2-broadening coefficients and pressure shift coefficients was estimated to about 4% and 11%, respectively. The O2-broadening coefficients obtained in the present work are compared with values reported in the literature for the ν5 band of CH3I, showing a satisfactory agreement with an average difference of about 8%. The shift coefficients are compared with values reported in the literature for the ν6 band of CH3F-Ar system, exhibiting the same order of magnitude and trend. The J and K rotational dependences of the O2-broadening coefficients have been observed and the latter modeled using empirical polynomial expansions. On average, the empirical expression reproduces the measured O2-broadening coefficients to within 3%. Using the measured broadening coefficients of the CH3I-O2 and CH3I-N2 Attafi et al., J Quant Spectrosc Radiat Transf 231 (2019) 1–8 systems, we produced CH3I-air broadening coefficients, ranging from 0.0783 to 0.1385 cm–1atm–1 at 295 K. The present results and the data already available should be valuable not only for predicting the CH3I infrared spectrum in the atmosphere, but also for verifying theoretical calculations of pressure-broadening and pressure-shift coefficients in the ν6 region of methyl iodide spectra.
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