Line Position Analysis Research Articles

Analysis of line positions of the ν6 band of 35ClNO2 around 411 cm−1

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.

Line Position and Line Intensity Modelings of H218O up to the First Triad and J = 20

Line position and line intensity analyses are carried out for the H218O isotopic species of the water molecule. Both datasets involve the five lowest lying vibrational states. For the line position analysis, the dataset includes infrared and far infrared transitions recorded in this work using high-temperature Fourier transform emission spectroscopy. Also included are already published infrared, far infrared, microwave, terahertz, Doppler-free combination differences, and kHz accuracy lines. The fitting is carried out with the bending–rotation approach and allows us to reproduce 12 858 line positions involving levels with J ≤ 20 and Ka ≤ 18, with a unitless standard deviation of 1.9, varying 207 spectroscopic parameters. For the line intensity analysis, far infrared line intensities measured in this work using Fourier transform spectroscopy in addition to previously measured line intensities are fitted. 5612 line intensities are accounted for with a unitless standard deviation of 1.5. The results from both analyses are used to build a line list for atmospherical purposes, spanning the 2–5000 cm−1 spectral range and containing 7593 lines. This line list and calculated energies and line intensities are compared to those already published.

Millimetre and sub-millimetre spectroscopy of doubly deuterated acetaldehyde (CHD2CHO) and first detection towards IRAS 16293-2422

Context. The abundances of deuterated molecules with respect to their main isotopologue counterparts have been determined to be orders of magnitude higher than expected from the cosmic abundance of deuterium relative to hydrogen. The increasing number of singly and multi-deuterated species detections helps us to constrain the interplay between gas-phase and solid-state chemistry and to understand better deuterium fractionation in the early stages of star formation. Acetaldehyde is one of the most abundant complex organic molecules (COMs) in star-forming regions and its singly deuterated isotopologues have already been observed towards protostars. Aims. A spectroscopic catalogue for astrophysical purposes is built for doubly deuterated acetaldehyde (CHD2CHO) from measurements in the laboratory. With this accurate catalogue, we aim to search for and detect this species in the interstellar medium and retrieve its column density and abundance. Methods. Sub-millimetre wave transitions were measured for the non-rigid doubly deuterated acetaldehyde CHD2CHO displaying hindered internal rotation of its asymmetrical CHD2 methyl group. An analysis of a dataset consisting of previously measured microwave transitions and of the newly measured ones was carried out with an effective Hamiltonian which accounts for the tunnelling of the asymmetrical methyl group. Results. A line position analysis was carried out, allowing us to reproduce 853 transition frequencies with a weighted root mean square standard deviation of 1.7, varying 40 spectroscopic constants. A spectroscopic catalogue for astrophysical purposes was built from the analysis results. Using this catalogue, we were able to detect, for the first time, CHD2CHO towards the low-mass proto-stellar system IRAS 16293-2422 utilising data from the ALMA Proto-stellar Interferometric Line Survey. Conclusions. The first detection of the CHD2CHO species allowed for the derivation of its column density with a value of 1.3×1015 cm−2 and an uncertainty of 10–20%. The resulting D2/D ratio of ~20% is found to be coincident with D2/D ratios derived for other COMs towards IRAS 16293-2422, pointing to a common formation environment with enhanced deuterium fractionation.

The 5.8 µm absorption bands for nitric acid (H14N16O3): line positions and intensities for the ν2 band at 1709.567 cm−1 and for its first associated hot bands (ν2+ν9−ν9, ν2+ν7−ν7, ν2+ν6−ν6)

This paper is the second of two back-to-back works, whose goal was to generate a more accurate linelist for the 5.8 µm absorption band of HNO3. Here, we report improved line positions and intensities in the ν2 cold band which is the main band in this region. For this, we recorded four high-resolution Fourier transform spectra for the ν2 band, centered at 1709.567 cm−1, under different experimental conditions. Using these spectra, a new extended line position analysis was performed for the ν2 band, leading to more accurate line positions. In parallel, individual line intensities were measured. It appears that, although the ν2 band is mainly of B-type, it also possesses a (very) weak A-type component that cannot be ignored. Overall, the line intensities in this new database are about 8% weaker than those quoted presently in the HITRAN (https://hitran.org/) or GEISA (https://geisa.aeris-data.fr/) databases. Our final linelist for HNO3 at 5.8 µm is provided as a supplement to this paper. It includes lines from the ν2 band together with those of the ν2+ν9−ν9, ν2+ν6−ν6, and ν2+ν7−ν7 associated hot bands that were generated during the first part of this study, described in the companion paper.

The rotation-torsion spectrum of CD2HOH

New transitions are reported in the submillimeter wave, terahertz, and far-infrared rotation-torsion spectrum of doubly-deuterated methanol CD2HOH. The newly assigned transitions allow us to spectroscopically characterize torsional states with 0⩽K⩽12 and 0⩽vt⩽2. Three line position analyses are carried out. In the first one, restricted to rotation-torsion lines involving torsional states with 3⩽K⩽12 and vt⩽2, rotational energies are evaluated with a J(J+1) Taylor-type expansion for each torsional state. 4853transitions were accounted for with a unitless standard deviation of 11.4. In the second analysis, 126torsional subband centers are fitted to obtain refined torsional parameters including the hindering potential. In the third analysis, 5911rotation-torsion transitions involving torsional states with vt⩽2, and J⩽26 are reproduced with a unitless standard deviation of 3.2 using a four-dimensional rotation-torsion fitting Hamiltonian.

Ro–vibrational analysis of the first hexad of hydrogen sulfide: Line position and strength analysis of the 4ν2 band of H232S and H234S for HITRAN applications

The high resolution infrared spectrum of hydrogen sulfide H232S was recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer and analyzed in the region of 4400–5400 cm−1 where ro–vibrational bands of the so–called first hexad of hydrogen sulfide are located. The present study is focused on the weak 4ν2 band. The 505 transitions with maximum values of the quantum numbers Jmax=17 and Kamax=8 (Jmax = 9 and Kamax=7 in the preceding studies) were assigned in the experimental spectrum. On this basis, 132 upper ro–vibrational energies (which is 2.5 times as high as in the preceding studies) were obtained. These data were used in the weighted fit of the Watson Hamiltonian parameters. The 28 varied parameters reproduce the 132 initial energy values with the root mean square deviation drms=3.5×10−4 cm−1. Strength analysis of the 287 strongest experimentally recorded transitions was made by the fit of their line shapes with the Hartmann-Tran profile. The eight effective dipole moment parameters of the 4ν2 band were obtained from the weighted fit which reproduce the initial experimental line strengths with the drms=3.1%. A comparison of the obtained results with the results of variational calculations and HITRAN data is presented. For the first time, transitions of the 4ν2 band of H234S were assigned in the experimental spectrum.

New analysis of line positions of the ν3 bands of 35ClNO2 and 37ClNO2 around 370 cm−1

A new investigation of the ν3 bands of 35ClNO2 and37ClNO2, located around 370 cm−1 has been performed using a high resolution (0.00102 cm−1) Fourier transform spectrum recorded at SOLEIL with highly improved experimental conditions as compared to previous work [Orphal J, Morillon-Chapey M, Klee S, Mellau GC, Winnewisser M. J Mol Spectrosc 1998;190:101–6]: (i) the use of synchrotron radiation which resulted in a better signal-to-noise ratio; (ii) a resolution twice better; (iii) a low temperature (221 K) with an optical path length of 8.16 m, allowing low pressure (0.025 hPa) in the sample leading to a well resolved spectrum. As a consequence, significantly better results than previously were obtained. Thanks to the new experimental conditions, the line assignments were pursued up to higher J and Ka quantum number values, J = 83 and Ka = 44. For both isotopomers, a total of 6331 transitions were reproduced with a root-mean-square deviation of 2 × 10−4 cm−1 using a Watson-type A-reduced Hamiltonian. Improved rotational and centrifugal distortion constants for the ν3 fundamental bands of 35ClNO2 and37ClNO2 have been determined. The band centers are 370.1510773(92) cm−1 for the ν3 fundamental band of 35ClNO2 and 364.5218094(96) cm−1 for the ν3 fundamental band of 37ClNO2. The synthetic line list obtained in this study could be interesting for future measurements of ClNO2 in the atmosphere, e.g. using the new space mission FORUM which is one of the concepts chosen by ESA to be developed further and which opens up a new window (150–1400 cm−1) for understanding and quantifying the radiative processes, as well as air quality and pollution effects.

Atlas of new and revised high-resolution spectroscopy of six CO isotopologues in the 101–115 nm range

Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observed spectra. The recent and future improvements of ultraviolet space instrumentation, both in sensitivity and resolution, require increasingly detailed laboratory molecular spectroscopy as a reference. As part of a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired gas-phase absorption spectra of six CO isotopologues in the vacuum ultraviolet. These spectra are recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a unique resolving power up to 106 in the 8–13 eV range. We have used resolutions in the 300 000–450 000 range for this campaign, which enable the analysis of individual line positions. We report new measurements on neighboring Rydberg states in the 101–115 nm range that could also be used as f-value calibrators, namely B1Σ+, C1Σ+, and E1Π, for six CO isotopologues. This range encompasses the absorption transitions B(v′ = 0, 1, and 2), C(v′ = 0, 1, 2, and 3), and E(v′ = 0, 1, 2, and 3) from X1Σ+(v′′ = 0). Higher resolution laser-based measurements of CO isotopologues from the literature are used to improve the absolute calibration and accuracy of our data. The overall uncertainty of the great majority of the line positions presented in this atlas is estimated to be 0.01 cm−1. In addition, some of the data derived from transition energies measurements, such as term values and molecular constants, are obtained for the first time, and others are improvements on previous sparser or lower spectral resolution datasets.

Line positions and intensities for the ν3 band of 5 isotopologues of germane for planetary applications

The germane molecule, GeH4, is present in the atmospheres of giant planets Jupiter and Saturn. The ongoing NASA mission Juno has renewed interest in its spectroscopy, whose accurate modeling is essential for the retrieval of other tropospheric species. We present here the first complete analysis and modeling of line positions and intensities in the strongly absorbing ν1/ν3 stretching dyad region near 2100 cm−1, for all five germane isotopologues in natural abundance. New infrared spectra were recorded, absolute intensities were extracted through a careful procedure and modeled thanks to the formalism and programs developed in the Dijon group. A database of calculated germane lines, GeCaSDa, has been build and is available online through the Virtual Atomic and Molecular Data Centre (VAMDC) portal and at http://vamdc.icb.cnrs.fr/PHP/gecasda.php.

New simultaneous fit of 12CD4 transitions in the 0–2400 cm−1 region

We report the global analysis of 12CD4 line positions from high-resolution rovibrational spectra, including accurate lines in the region 0–2400 cm−1. In addition to the lines of P0–P0 and P1–P1 (where P0 is the ground state (GS), and P1 is the dyad (ν2, ν4)), this region covers two cold polyads: P1 (900–1220 cm−1, two vibrational levels, two sublevels) and the pentad (2ν4, ν2 + ν4, ν1, 2ν2, ν3) or P2 (1850–2400 cm−1, five vibrational levels, nine sublevels). In this analysis, 2724 assignments from four sources are fitted using an effective Hamiltonian expanded up to the sixth order for the pentad. For the assignments and analysis, we use the SPVIEW and XTDS software programs that implement the tensorial formalism developed in the Dijon group for tetrahedral molecules. Among the 454 parameters of the effective Hamiltonian for the pentad (of which 10 are relative to the GS (or P0) and 72 are relative to the dyad), 233 were fitted (10 of which are GS and 37 of which are dyad). The 47 parameters for the dyad and the 233 parameters for the pentad allow very good simulations to be made. For this study, a total of 2724 line positions were used in the least squares adjustment characterized by the following global root mean square deviations dRMS for line positions: 0.01 × 10−4 cm−1 for P0–P0, 0.4 × 10−4 cm−1 for P1–P1, 1.3 × 10−4 cm−1 for the dyad, and 0.7 × 10−4 cm−1 for the pentad. XTDS and SPVIEW, which can simulate spectra, allowed us to verify and compare the calculated spectrum, to the experimental spectrum for the dyad and pentad regions of 12CD4 and to a spectrum obtained from variational calculation and from ab initio DMS (TheoReTS information system http://theorets.univ-reims.fr or http://theorets.tsu.ru ).

High resolution study of MSiH4 (M=28, 29, 30) in the Dyad Region: Analysis of line positions, intensities and half-widths

The infrared spectra of SiH4 in natural abundance (92.23% of 28SiH4, 4.68% of 29SiH4, and 3.09% of 30SiH4) were measured in the region of 600–1200cm−1 with a Bruker IFS 120HR Fourier transform spectrometer, analyzed and compared with the results available in the literature. More than 3500 transitions with Jmax.=27 were assigned to the dyad bands ν4 and ν2 of 28SiH4 (the band ν2 is allowed in Raman, but forbidden in absorption spectra for symmetry reasons, and its transitions appear in absorption spectra only because of strong Coriolis interaction with the ν4 band). Rotational, centrifugal distortion, tetrahedral splitting, and interaction parameters for the ground, (0100) and (0001) vibrational states were determined from the fit of experimental line positions. The obtained set of parameters reproduces the initial experimental data with accuracy close to experimental uncertainties. The results of the analogous analyses of the 29SiH4 and 30SiH4 isotopologues are also presented (the numbers of the assigned transitions are here more than 1360 and 1120). An further analysis of about 790 experimental ro-vibrational lines in the dyad region of 28SiH4 was performed using the Voigt profile to simulate the measured line shape and to determine experimental line intensities. A set of 4 effective dipole moment parameters for the dyad of 28SiH4 was obtained on that basis from the weighted fit, which reproduce the initial experimental intensities of about 790 lines with the drms=5.6%. Analogous analyses were made for the two other isotopic species, 29SiH4, and 30SiH4. A detailed line list of transitions in the region of 750–1150cm−1 is generated. The half-widths of 40 ro-vibrational lines (Jup.max.=16) are studied from the multi-spectrum analysis, and self-pressure broadening coefficients are determined.

The bending potential energy function of HDO obtained from high-resolution data

Line position and line intensity analyses of the high-resolution spectrum of the HDO isotopic species of the water molecule are performed with an extended version of the Bending-Rotation approach up to the (010) state and J=22. The line position analysis involves 3992 microwave, far infrared and infrared lines, and 421 experimental energy levels which were reproduced with a 1.1 unitless standard deviation. The data set considered in the line intensity analysis consists of 1405 infrared absorpon lines and 4 Stark coefficients fitted with a 1.2 unitless standard deviation. The results of both analyses are compared with previous investigations and are used to build a spectroscopic database which is compared with other available databases and should be useful for interpreting measurements carried out with the Infrared Atmospheric Sounding Interferometer (IASI).

High-resolution spectroscopy of the bands in 13C18O: term values, ro-vibrational oscillator strengths and Hönl–London corrections

Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observations. The constant improvement in UV space instrumentation, both in sensitivity and resolution, requires increasingly detailed laboratory data. Following a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired complete datasets on the CO isotopologues in the vacuum ultraviolet. Absorption spectra were recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a resolving power R > 106 in the 8–12 eV range. Such resolution allows the analysis of individual line positions and strengths in electronic transitions and the location of perturbations. We continue our previous work on A–X bands of 12C16O and 13C16O, reporting here measurements for the 13C18O isotopologue. Gas column densities in the differentially-pumped system were calibrated using the B–X ) band. Absorption bands are analyzed by synthesizing line and band profiles and fitting them to measured spectra. New results for A–X) bands include precise line assignments, term values, band-integrated oscillator strengths as well as individual ro-vibrational oscillator strengths and Hönl–London corrections. For () our results are compared with earlier studies. The interpretation of mixed perturbing bands, complementing an earlier study, is also presented as well as precise line assignments and term values for the B–X(0–0) band calibrator, and the nearby B–X (1–0) and C–X(0–0) bands.

Line position analysis of the ν2 band of SO2F2 using the C2vTop Data System

A new high-resolution infrared spectrum of the ν2 band of SO2F2 centered at 849.46cm−1 has been recorded with a resolution of 0.00102cm−1 at the AILES beamline of SOLEIL Synchrotron facility. More than 1600 lines up to Jmax=41 have been assigned and fitted in line position using a tensorial formalism adapted to the case of XY2Z2 asymmetric molecules developed as an extension of the usual one used for spherical tops (Rotger et al., 2002). The analysis has been performed in the O(3)⊃Td⊃C2v group chain, thanks to the C2vTDS program suite (Wenger et al., 2005). This approach allows a systematic development of rovibrational interaction to study any polyad of SO2F2 and makes easier global analysis. Compared to a previous study (Merke et al., 2006), the present fit uses less effective Hamiltonian parameters but we assigned lines up to a lower J value.

New analysis of the ν6 and 2ν3 bands of methyl iodide (CH3I)

A new rovibrational study of the ν6 band of methyl iodide was conducted to obtain a rather complete line list. A new analysis of line positions was accomplished. The spectrum of this band has been first recorded using the Bruker IFS125HR Fourier transform spectrometer (FTS) at the AILES beamline of the SOLEIL Synchrotron facility and later with the Bruker IFS125HR FTS located at the LISA facility in Créteil. Altogether, about 10,000 lines were assigned for the ν6 and 2ν3 bands up to high quantum numbers (J⩽85 and K⩽20). Because of the large value of the 127I nuclear quadrupole hyperfine constant, a significant portion of these assignments concerns clusters of hyperfine subcomponents, which are easily observable at 11μm. These infrared data were combined in a least squares fit together with the existing microwave data on rotational transitions within the v6=1 and v3=2 vibrational states to get the upper state rotational constants and interacting parameters for the v6=1 and v3=2 states. Due to the high values of quantum numbers achieved during this infrared analysis, the final energy level calculation accounts for aCx(Δℓ=±1;ΔK=±1) and an α(Δℓ=∓1;ΔK=±2) types of Coriolis interactions coupling the v6=1 energy levels with those from the v3=2 and v2=1 states, respectively. On the other hand, it proved unnecessary to update the existing hyperfine parameters for the v6=1 and v3=2 states.

High‐resolution stimulated Raman spectroscopy and analysis of line positions and assignments for the ν2 and ν3 bands of 13C2H4

High‐resolution stimulated Raman spectra of13C2H4 in the regions of the ν2 and ν3 Raman active modes have been recorded at two temperatures (145 and 296 K) based on the quasi continuous‐wave (cw) stimulated Raman spectrometer at Instituto de Estructura de la Materia IEM‐CSIC in Madrid. A tensorial formalism adapted to X2Y4 planar asymmetric tops with D2h symmetry (developed in Dijon) and a program suite called D2hTDS (now part of the XTDS/SPVIEW spectroscopic software) were proposed to analyze and calculate the high‐resolution spectra. A total of 103 and 51 lines corresponding to ν2 and ν3 Raman active modes have been assigned and fitted in wavenumber with a global root mean square deviation of 0.54 × 10−3 and 0.36 × 10−3 cm−1, respectively. Due to the fact that the Raman scattering effect is weak, we did not perform in this contribution the line intensities analysis. Copyright © 2016 John Wiley & Sons, Ltd.

Line position and line intensity analyses of the high-resolution spectrum of H218O up to the First Triad and [formula omitted

Line position and line intensity analyses of the high-resolution spectrum of the H218O isotopic species of the water molecule are performed with the Bending-Rotation approach up to J=17 and the First Triad of interacting states, (020), (100), and (001). The line position analysis involves microwave and terahertz transitions, ground state combination differences, far infrared and infrared lines, and experimental energy levels which were reproduced with a 1.2 unitless standard deviation. The data set considered in the line intensity analysis consists of 3707 infrared transitions recorded using absorption spectroscopy at room temperature which were fitted with a 1.4 unitless standard deviation. The results of both analyses are compared with previous investigations and are used to build a line position and line intensity database to update the HITRAN and GEISA databases. A comparison with the HITRAN 2012 database reveals that the new database yields intensity values closer to the experimental ones.

Spin-torsion effects in the hyperfine structure of methanol.

The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.

Study of the ν3 band of 12CD4: Line position analysis and unambiguous fit of q2J4 terms

We report the analysis of 12CD4 line positions from high-resolution rovibrational spectra, including accurate lines in the region 2160–2360cm−1. In this analysis, 181 data points are fitted using an effective Hamiltonian expanded up to the sixth order for the ν3 fundamental band. For the assignments and analysis, we use the SPVIEW and XTDS software programs that implement the tensorial formalism developed in the Dijon group for tetrahedral molecules. Experimental transitions are assigned up to J⩽15 for the ν3 cold band. Among the 37 parameters of the effective Hamiltonian for the ν3 fundamental band (of which 10 are relative to the Ground State (GS or P0), and 27 are relative to ν3), 22 relative to ν3 were fitted. The 32 parameters for ν3 allow very good simulations to be made. For this study, a total of 181 line positions were used in the least squares adjustment characterized by the root mean square deviation dRMS for line positions: 1.196×10−3cm−1. On the basis of our set of 181 fits of experimental data for ν3 of 12CD4, the ambiguity of effective Hamiltonians for triply degenerate F2 states of tetrahedral molecules is verified. It is shown that, in agreement with theory, any of q2J4-type parameters cannot be determined from experimental data in a unique way, and these parameters cannot be considered as spectroscopic constants.

Line position analysis of the high resolution infrared spectrum of 12CD4 in the region from 900 to 2400 cm−1

We report the global analysis of 12CD4 line positions from high-resolution rovibrational spectra, including accurate lines in the region 900–2400cm−1. This covers two cold polyads: the Dyad (ν2, ν4) or P1 (900–1220cm−1, 2 vibrational levels, 2 sublevels) and the Pentad (2ν4, ν2+ν4, ν1, 2ν2, ν3) or P2 (1850–2400cm−1, 5 vibrational levels, 9 sublevels). In this analysis, 2308 data points from three sources are fitted using an effective Hamiltonian expanded up to the fourth order for the Pentad. For the assignments and analysis, we use the SPVIEW and XTDS software programs that implement the tensorial formalism developed in the Dijon group for tetrahedral molecules. Experimental transitions are assigned up to J⩽20 for the Dyad and Pentad cold bands. Among the 206 parameters of the effective Hamiltonian for the Pentad (of which 10 are relative to the Ground State (GS or P0) and 72 are relative to the Dyad), 125 were fitted (8 of which are GS and 40 of which are Dyad). The 48 parameters for the Dyad and the 125 parameters for the Pentad allow very good simulations to be made. For this study, a total of 2308 line positions were used in the least squares adjustment characterized by the following global root mean square deviations dRMS for line positions: 6.2×10−4cm−1 for the Dyad and 3.8×10−4cm−1 for the Pentad. This paper presents a reanalysis of 12CD4 infrared absorption data in order to perform a global fit of line positions for two polyads of this molecule.