Ν3 Band Research Articles

Analysis Of Micro-Raman Spectroscopy and Optical Band Gap Energy Of LiMnxFe1-xPO4 Cathode Materials Prepared According To Hydrothermal Route

LiMnxFe(1-x)PO4 olivine cathode material (x= 0.1; 0.2; 0.3 and 0.8) fabricated according to hydrothermal route. Micro-Raman spectroscopy, SEM scanning electron microscopy, UV-Vis absorption spectra and reflectance spectra methods were performed to study the characteristics of materials. The results showed that LiMnxFe(1-x)PO4 prepared materials were nano-meter in size (60-100 nm) and distorted sphere-like shape. The material has bands in the Raman spectrum corresponding to the position of the bands of the pure LiFePO4 and shift slightly. The band position at 410 cm-1 (corresponding to the position of the n2 band of the pure LiFePO4 sample) was attenuated of the sample in which Mn2+ ion content replaced Fe2+ ion content to 0.8 molar ratio. But the band position at 1020 cm-1 appeared with Strengthening intensity (corresponding to the position of the n3 band of the pure LiMnPO4 sample). The optical band gap energy of samples determined according to the Tauc equation in the range of 3.33-3.5 eV.

O2- and N2-broadening parameters in the ν3 and 2ν3-ν3 bands of methyl chloride

In this paper, we report high-resolution measurements of oxygen and nitrogen pressure-broadening coefficients for ro-vibrational transitions in the ν3 and 2ν3-ν3 bands of methyl chloride (CH335Cl and CH337Cl). We present the first high-resolution measurement of oxygen broadening coefficients for the CH3Cl, along with an extensive determination of the nitrogen broadening coefficients in the ν3 band which complements the measurements made by diode laser spectrometer in previous works. For the 2ν3-ν3 band, the oxygen and nitrogen broadening coefficients are measured here for the first time. The results have been obtained by analyzing fourteen spectra with a mono-spectrum non-linear least squares fitting of Voigt profile using data recorded at 295 K at the AILES beamline of the SOLEIL Synchrotron facility using a Bruker IF125HR Fourier transform spectrometer. Broadening coefficients of 1793 and 1732 lines in both bands of both isotopes of CH3Cl for O2 and N2 buffer gases respectively have been retrieved. The rotational dependences of these coefficients have been modeled using an empirical model, which reproduces the measured data with a difference of about 6 %. Using the measured values of O2- and N2-broadenings, we derived the Air-broadening coefficients. Finally, comparisons with previous works are performed.

Infrared Spectrum of the Adamantane+ -Water Cation: Hydration-Induced C-H Bond Activation and Free Internal Water Rotation.

Diamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C−H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C10H16 +–H2O, Ad+–W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion‐corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn–Teller distorted Ad+ via a strong CH⋅⋅⋅O ionic H‐bond supported by charge–dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad+ in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν3 band of W, resulting from weak angular anisotropy of the Ad+–W potential.

Infrared Spectrum of the Adamantane+–Water Cation: Hydration‐Induced C−H Bond Activation and Free Internal Water Rotation

AbstractDiamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C−H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C10H16+–H2O, Ad+–W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion‐corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn–Teller distorted Ad+via a strong CH⋅⋅⋅O ionic H‐bond supported by charge–dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad+in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν3band of W, resulting from weak angular anisotropy of the Ad+–W potential.

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.

High-resolution spectroscopy and analysis of the ν3, ν4 and 2ν4 bands of SiF4 in natural isotopic abundance

Silicon tetrafluoride (SiF4) is a trace component of volcanic gases. However, a better knowledge of spectroscopic parameters is needed for this molecule in order to derive accurate concentrations. This motivated FTIR measurements with high-spectral resolution (0.001 cm−1) and an extensive study of its infrared absorption bands, including the fundamentals and overtone and combinations. We present here a detailed analysis and modeling of the strongly absorbing ν3and ν4 fundamental bands, for the three isotopologues in natural abundance: 28SiF4 (92.23 %), 29SiF4 (4.67 %) and 30SiF4 (3.10 %). It includes a global fit with consistent parameter sets for the ground and excited states. In particular, all existing rotational line data have been included. The 2ν4 band of 28SiF4 could also be analyzed in detail. A first fit of the dipole moment derivative for the ν3 band for 28SiF4 has been performed, along with two independent estimates of the integrated band intensity; the results are consistent with literature values, around 690 km/mol. The isotopic dependence of band centers and Coriolis parameters has also been studied. TFSiCaSDa, a new database of cross sections and calculated lines for the ν3 band of SiF4, has been set up.

Vibrational dependence, temperature dependence, and prediction of line shape parameters for the H2O-N2 collision system

In a recent work [JQSRT 228,79(2019)], Vispoel et al. optimized the intermolecular potential used in the Modified Complex Robert-Bonamy (MCRB) formalism for the H2O-N2 collision system. Calculations were made for a number of transitions in the rotation and ν2 bands. The needs of the spectroscopic and astrophysics communities include data for water vapor transitions that have multiple vibrational quanta exchanged. In this work, MCRB calculations were made for 0–4 vibrational quanta exchanged in the ν1, ν2, and ν3 bands for 13 temperatures from 200–3000 K; 7272 transitions for each band. From these data, the vibrational and temperature dependence of the half-width and line shift were determined. The temperature dependence was determined using the Gamache-Vispoel model [JQSRT 217, 440(2018)]. The data allowed the development of a routine that can predict the half-width, line shift, and their temperature dependence for transitions not yet studied. The prediction algorithm is based on theory [JQSRT, 83, 119(2004)] and yields line shape parameters with much smaller uncertainty than obtained by fitting with ad hoc polynomials or J” averaged values. A line file based on the 2020 update to the HITRAN2016 water vapor line file was created with N2 as the broadening species. These data are useful for combustion studies and as a first step to determining air-broadening for the HITRAN and GEISA databases.

Comprehensive ro–vibrational analysis of di–deuterated hydrogen sulfide in the region of the ν2, 2ν2 and [formula omitted] bands: The D232S, D234S, and D233S isotopologues

High–resolution infrared spectra of the D2S molecule were experimentally recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer and theoretically analyzed in the region of 700 – 1800 cm−1, where the ν2 and 2ν2 bands are located. For the first time, transitions were assigned to the 2ν2 and 2ν2−ν2 bands of the D232S and D234S isotopologues. For the ground vibrational state and the ν2 band of D234S, the spectral information was considerably extended in comparison with preceding works. For the first time, transitions belonging to the rare D233S hydrogen sulfide species were assigned to the ν2 and 2ν2 bands, as well as a rotational structure of the ground vibrational state of D233S was determined on the basis of experimental values of the ground state combination differences (maximum values of quantum numbers for used ground state combination differences were Jmax=19,Kamax=8,ΔJmax=2,ΔKamax=2). Sets of spectroscopic parameters of the Watson hamiltonian in A−reduction and Ir−representation was determined for the (010) and (020) vibrational states of all three discussed species and for the ground vibrational states of D234S and D233S from the weighted fit of parameters of this hamiltonian. The drms of reproduction of the initial experimental data for all nine vibrational states (three vibrational states for any species) is not far from 1×10−4 cm−1 which is close to experimental errors in line positions.

Line intensity parameters in the ν3 and 2ν3-ν3 bands of methyl chloride in the 13 µm region

We performed the systematic measurements of line intensities of ro-vibrational absorption transitions of the ν3 and 2ν3-ν3 parallel bands of 12CH335Cl and 12CH337Cl isotopes. The spectra were recorded in the spectral region between 650 and 800 cm−1 with a high-resolution Fourier transform spectrometer.A mono-spectrum fitting technique was used to fit a series of seven spectra at pressures of CH3Cl ranging from 1.02 to 10.24 mbar to retrieve line intensities of 2385 transitions of the two isotopic species. The measured line intensities are discussed in relation to rotational quantum numbers, and used to derive the square of the transition dipole moments for each line. The analysis of these moments allows us to derive a consistent set of line intensity parameters, such as vibrational transition moments, band intensities as well as Herman-Wallis coefficients for both bands. The results of the ν3 band are in satisfactory agreement with previous works and present databases, but a larger discrepancy (≈ 30%) is observed for the 2ν3-ν3 hot band.

Mode-specific vibrational predissociation dynamics of (HCl)2 via the free and bound HCl stretch overtones.

Velocity-map ion imaging has been used to study the vibrational predissociation dynamics of the HCl dimer following infrared (IR) excitation in the HCl stretch overtone region near 1.77 Å. HCl monomer predissociation products were detected state-selectively using 2 + 1 resonance-enhanced multiphoton ionization spectroscopy. The IR action spectrum shows the free HCl stretch (2ν1), the bound HCl stretch (2ν2), and a combination band involving the intermolecular van der Waals stretching mode (2ν2 + ν4). Fragment speed distributions extracted from ion images obtained for a range of HCl(v = 0, 1; J) levels following vibrational excitation on the 2ν1 and 2ν2 bands yield the correlated product pair distributions. All product pairs comprise HCl(v = 1) + HCl(v = 0) and show a strong propensity to minimize the recoil kinetic energy. Highly non-statistical and mode-dependent HCl product rotational distributions are observed, in contrast to that observed following stretch fundamental excitation. Predissociation lifetimes are also mode-dependent: excitation of the free HCl leads to τVP = 13 ± 1 ns, while the bound stretch has a shorter lifetime τVP ≤ 6 ns. The dimer dissociation energy determined from energy conservation (D0 = 397 ± 7 cm-1) is slightly smaller than the previously reported values. The results are discussed in the context of previous observations for (HF)2 and (HCl)2 after excitation of HX stretch fundamentals and models for vibrational predissociation.

High-resolution FTIR spectroscopy of 12C2HD3 in the 830–1110 cm−1 region: A study of the Coriolis and anharmonic interactions within the v3 = 1, v6 = 1 and v8 = 1 triad

The infrared spectrum of ethylene-d3 (12C2HD3) was measured between 830 and 1110 cm-1, covering the ν3, ν6 and ν8 bands, using a Fourier transform infrared (FTIR) spectrometer at an unapodized resolution of 0.0019 cm−1. The three upper vibrational states were found to mutually-interact through Coriolis and anharmonic resonances. A total of 2128 a- and b-type absorption lines of the ν3 band and 3107c-type lines of the ν8 band were assigned in this work. Although the ν6 band is relatively weak, 246 spectral lines were identified and included in the final fit for the rovibrational parameters of the upper vibrational states. Using a Hermitian Hamiltonian comprising Watson's-type rotational operators and off-diagonal interaction terms, three sets of rovibrational constants up to quartic terms were derived for the v3 = 1, v6 = 1 and v8 = 1 states together with thirteen interaction parameters, with a root-mean-square (rms) deviation of the fit = 0.00059 cm−1. The band centres of the ν3, ν6 and ν8 bands were determined to be 1044.260675 ± 0.000025 cm−1, 998.60182 ± 0.00060 cm−1 and 918.732573 ± 0.000019 cm−1 respectively. A set of ground state rovibrational constants of 12C2HD3 up to five quartic constants was also derived with improved precision from a simultaneous fit of 782 ground state combination differences (GSCDs) from a-type infrared transitions of the ν3 band and 1422 GSCDs from the c-type ν8 band from the present analysis, together with 377 GSCDs from the previous work on the 2ν8 band. The rms deviation of the GSCD fit was 0.00039 cm-1. The experimental spectroscopic parameters compare favourably with the quantum-chemically calculated values at the MP2/cc-pVQZ and B3LYP/cc-pVQZ levels of theory.

Measurements and calculations of Kr-broadening and shift parameters of water vapour transitions in a wide spectral region

The water vapour line broadening (γ) and shifting (δ) coefficients for 497 lines of 16 vibrational bands ν1, ν3, 2ν2, ν1 + ν2, ν2 + ν3, 3ν2, 2ν2 + ν3, ν1 + 2ν2, ν1 + ν3, 2ν1, 2ν3, 6ν2, 2ν1 + ν2,ν2 + 2ν3, ν1 + 3ν2, and 3ν2 + ν3 induced by krypton pressure were measured with Bruker IFS 125 HR Fourier transform spectrometer. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm−1 and in a wide pressure range of Kr (0.303–0.980 atm). The calculations of the broadening and shift coefficients γ and δ were performed in the framework of the semi-classical method. The intermolecular potential was taken as the sum of the anisotropic atom–atom potential and the vibrationally and rotationally dependent isotropic Lennard-Jones potential. The measured coefficients γ and δ were combined with literature data for the ν2 and rotational bands, and optimal sets of potential parameters that gave the best agreements with the measured broadening coefficients for each vibrational band separately were found. Experimental data for ten vibrational bands of H2O perturbed by Kr were used to determine the analytical dependence of some of the potential parameters on the vibrational quantum numbers. Combined experimental data for the coefficients γ of 19 vibrational bands of H2O perturbed by Kr were fitted to the empirical function. The computed coefficients γ and δ derived from the semi-classical method and the fitted parameters were compared statistically to the measurements. The vibrational dependence of the potential as well as of the coefficients γ and δ is discussed.

The H2O Spectrum of the Massive Protostar AFGL 2136 IRS 1 from 2 to 13 μm at High Resolution: Probing the Circumstellar Disk

Abstract We have observed the massive protostar AFGL 2136 IRS 1 in multiple wavelength windows in the near- to mid-infrared at high (∼3 km s−1) spectral resolution using VLT+CRIRES, SOFIA+EXES, and Gemini North+TEXES. There is an abundance of H2O absorption lines from the ν 1 and ν 3 vibrational bands at 2.7 μm, from the ν 2 vibrational band at 6.1 μm, and from pure rotational transitions near 10–13 μm. Analysis of state-specific column densities derived from the resolved absorption features reveals that an isothermal absorbing slab model is incapable of explaining the relative depths of different absorption features. In particular, the strongest absorption features are much weaker than expected, indicating optical depth effects resulting from the absorbing gas being well mixed with the warm dust that serves as the “background” continuum source at all observed wavelengths. The velocity at which the strongest H2O absorption occurs coincides with the velocity centroid along the minor axis of the compact disk in Keplerian rotation recently observed in H2O emission with ALMA. We postulate that the warm regions of this dust disk dominate the continuum emission at near- to mid-infrared wavelengths, and that H2O and several other molecules observed in absorption are probing this disk. Absorption line profiles are not symmetric, possibly indicating that the warm dust in the disk that produces the infrared continuum has a nonuniform distribution similar to the substructure observed in 1.3 mm continuum emission.

Ro–vibrational analysis of the 12C2H2D2-cis molecule spectra in the region of 1150–1450 cm[formula omitted]: The ν12, ν3, 2ν10 and [formula omitted] bands

High–resolution infrared spectra of the 12C2H2D2-cis molecule were analyzed in the region of 1150–1450 cm−1, where the strongly interacting ν12(B1), ν3(A1), 2ν10(A1) and ν8+ν10(A2) bands are located. For these four bands 5594 transitions with maximum values of quantum numbers Jmax=50 and Kamax=21 were assigned. This number is more than 2.7 times higher than in previous studies; transitions of the ν3 and ν8+ν10 bands have been assigned for the first time. The obtained information was used in the weighted fit with the goal to determine parameters of the effective Hamiltonian. The obtained set of 89 varied parameters reproduces the 1546 initial ro–vibrational energies (5594 transitions) with the drms=2.59×10−4 cm−1. A list of the assigned transitions is presented as the Supplementary material.

Depolarization Ratios of Methane Raman Bands as a Function of Pressure

In this work, we measured the intensities of Q-branches of the ν1, ν2 and ν3 bands in the polarized and depolarized methane Raman spectra in the pressure range of 1–60 atm. It was established that the pressure dependence of depolarization ratios of the ν2 and ν3 bands are negligible. In turn, the depolarization ratio of the ν1 band increases with increasing pressure and reaches approximately 0.0045 at 60 atm. These data are more precise than previously published ones because ν1 band intensities were determined taking into account the contribution of overlapping lines of ν3 band. The presented data will be useful in calculating the methane polarizabilities at high pressure, as well as in calculating methane Raman spectra for measuring the natural gas composition using Raman spectroscopy.

Ferrimagnetic to antiferromagnetic transition and complex impedance analysis of Cr-doped magnesium ferrite nanoparticles

The chromium-doped magnesium ferrite (MgCrxFe2−xO4, x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0) were prepared using sol–gel technique. X-ray diffraction scans confirmed the cubic spinel structure for all the nanoparticles samples. Reduction in lattice parameter and average crystallite size with increasing Cr3+ concentration was observed due to smaller ionic radii of Cr3+ (0.67 A) ions as compared to Fe3+ (0.63 A) ions. In FTIR vibrational studies, the addition of Cr3+ shows the splitting of ν1 band into two sub-bands due to variation of bond strength between same cations present at tetrahedral and octahedral lattice sites. With increasing Cr3+ concentration, the ZFC–FC magnetic curves revealed a ferrimagnetic (FiM) to antiferromagnetic (AFM) transition as compound transformed from MgFe2O4 to MgCr2O4. The M–H loops revealed decrease in saturation magnetization with increase in Cr3+ concentration which is attributed to FiM to AFM transition. The coercivity showed a non-monotonic behavior and has maximum value of 750 Oe for x = 1.2 due to overlapping of blocking and Neel transition temperatures. The dielectric properties showed a decreasing trend with increasing Cr3+ concentration. The room temperature impedance spectroscopy (Nyquist plots) was simulated using equivalent RC circuit model and an appearance of second semi-circle in the Nyquist plot with increasing Cr3+ concentration is observed which can be attributed to the contribution of grains in the hooping mechanism.

Improved ground state and [formula omitted] = 1 state rovibrational constants of formaldoxime (CH2NOH)

The high-resolution Fourier transform infrared (FTIR) spectrum of the ν12 band of formaldoxime (CH2NOH) was recorded at the Australian Synchrotron with an unapodized resolution of 0.0018 cm−1 in the 320–460 cm−1 region. A total of 1895 infrared transitions were fitted using the Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.000156 cm−1. From this rovibrational analysis, the ν12 = 1 state rotational constants (A and C) and five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) were improved from previous work and three sextic terms (ΦJK, ΦKJ, ΦK) were derived for the first time. The band center of the ν12 band of CH2NOH was found to be 397.685235(23) cm−1. All five quartic centrifugal distortion terms of the ground state were also improved with higher accuracy. The ground state ΦJK, ΦKJ, ΦK were obtained for the first time through the fitting of 1501 ground state combination differences (GSCDs) derived from the IR transitions of the ν12 and ν10 bands, together with 23 previously reported microwave frequencies. The rms deviation of this GSCD fit was 0.000687 cm−1. Additionally, rotational constants and higher order centrifugal distortion terms of the ground and v12 = 1 states were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set, for comparison with the experimental results. The calculated and experimental rovibrational constants of CH2NOH for both ground and v12 = 1 states were in good agreement.

The fundamental [formula omitted] band of DTO and the [formula omitted] overtone band of HTO from the analysis of a high-resolution spectrum of tritiated water vapour

The ν3 fundamental band of DTO and the 2ν1 overtone band of HTO have been analysed for the first time from a high-resolution infrared spectrum of tritiated water vapour recorded at room temperature using a Bruker IFS 125HR Fourier transform spectrometer applying a resolution of 0.0075cm-1.For DT16O, we report 436 new experimental line positions in the 2500–2900cm-1 range that were assigned to the ν3 band, with rotational quantum numbers up to J=15 and Ka=8. For HT16O, we report 361 new experimental line positions in the 4300–4700cm-1 range that were assigned to the 2ν1 band, with rotational quantum numbers up to J=15 and Ka=7.For both species the assigned lines were used to determine the spectroscopic constants in the A-reduced Watson Hamiltonian. No perturbations were observed.The comparison with variational calculations of line positions and intensities from the Tomsk database shows differences of up to several 0.1cm-1 concerning the line positions, while the relative line intensities agree with the observed values within a few percent.The line list from this study will be useful for detection of gaseous traces of HTO using laser-based methods in the future and further serve the completion of experimental line lists.

High-resolution investigation of temperature and pressure-induced spectroscopic parameters of 13C-isotopomer of CH4 in the ν4 band using cavity ring-down spectroscopy

Measurements of high-resolution spectroscopic line parameters in the ν4 fundamental band of 13CH4 isotopomer of methane (CH4) occurring at 7.5 µm mid-IR spectral region are important for the studies of remote sensing of the Earth and planetary atmospheres at different conditions. Here, a continuous wave (cw) external-cavity quantum cascade laser (EC-QCL) coupled with cavity ring-down spectroscopy (CRDS) technique has been employed to probe the ν4 (F2) fundamental band of 13CH4 isotopomer. We recorded the high-resolution CRD spectra of 22 interference-free transition lines in the P, Q and R-branches of 13CH4 and subsequently determined the symmetry-specific line parameters such as line-intensity, pressure broadening coefficients along with temperature dependence of broadening coefficients of the transition lines. Our study thus provides more accurate experimental evidences of the high-resolution spectral features of 13CH4 isotopomer with rotational symmetry (A, E, F) for the ν4 (F2) band at wavelengths near 7.5 µm for a range of temperatures.

Spectroscopy of a low global warming power refrigerant. Infrared and millimeter-wave spectra of trifluoroethene (HFO-1123) in the ground and some vibrational excited states

In the present work we carried out a combined rotational and ro-vibrational investigation on 1,1,2-trifluoroethene, a relevant unsaturated hydrofluoroolefin recently proposed as refrigerant in mixture with other halogenated compounds (like difluoromethane). By employing a frequency-modulation millimeter-wave spectrometer, the rotational spectra were recorded in the frequency ranges 80–96 GHz and 245–260 GHz for the ground and also the vibrationally excited states ν8=1,ν9=1,ν12=1,ν9=2,ν12=2, and ν9=ν12=1. In addition, the infrared spectra in the region of the ν6 band (centered at 929.8cm−1) were measured with a high-resolution Fourier transform spectrometer. The data coming from the detailed rotational and ro-vibrational assignments were combined in a global fit, taking into account also the ground state transitions available in the literature. From this analysis, a very accurate set of rotational and centrifugal distortion constants was determined for the ground state and for all the vibrationally excited states here investigated.