High Resolution Study of Deuterated Hydrogen Sulfide in the Region 2400-3000 cm

High resolution Fourier transform spectra of deuterated hydrogen sulfide have been recorded in the region 2400-3000 cm⁻¹. Rotational structures of the ν₁ + ν₂, ν₂ + ν₃ bands of D₂³²S, of the ν₃ and ν₁ + ν₂ bands of HD³²S, and of the ν₁ + ν₂ band of HD³⁴S were analyzed. Band centers and rotational, centrifugal distortion, and resonance parameters were obtained, which reproduce the initial values of the upper energy levels within a mean accuracy of 1.39 × 10⁻⁴ cm⁻¹ for the states (110) and (011) of D₂³²S, 1.61 × 10⁻⁴ cm⁻¹ and 1.82 × 10⁻⁴ cm⁻¹ for the states (001) and (110) of HD³²S, and 2.09 × 10⁻⁴ cm⁻¹ for the state (110) of HD³⁴S, respectively.     

Infrared spectral study of molecular vibrations in amorphous, nanocrystalline and AlO(OH) · αH2O bulk crystals

Amorphous, nanocrystalline, and bulk AlO(OH) · xH₂O crystals have six fundamental modes (FM) of vibration in a nonlinear AlO(OH) molecular structure. Most of them appear in groups of four IR and Raman bands. Their positions and relative intensities differ significantly in three specimens. The nanocrystals (monoclinic structure with z=8 molecules per unit cell) have four OH stretching bands at values enhanced by up to 360 cm⁻¹ at 3120, 3450, 3560 cm⁻¹ in comparison to those in bulk crystals or amorphous specimens. The first two bands are broad, bandwidth Δν_1/2200 to 350 cm⁻¹, while the other two are sharp, Δν_1/290 cm⁻¹. The sharp bands shift to 3525 and 3595 cm⁻¹ after heating the sample at 100°C. They no longer appear after heating at 300 or 500°C for 2 h (the specimen decomposes to Al₂O₃), leaving behind only two bands at 3100 and 3400 cm⁻¹. A Δν_1/2 value of 500 cm⁻¹ appears in the 3400 cm⁻¹ in a delocalized distribution of H atoms. Two bands also occur at 3098 and 3300 cm⁻¹ in bulk crystals (orthorhombic structure with z=4) or at 2990 and 3515 cm⁻¹ in an amorphous sample. More than one bands appear in a FM vibration in occurrence of sample in more than one conformers. The amorphous sample has approximately the same conformer structure as the bulk crystals. An amorphous surface structure exists in nanocrystals with a group of three bands at 1420, 1510 and 1635 cm⁻¹ in an interconnected network structure. It encapsulates the nanocrystals in an amorphous shell. Its volume fraction, 33% estimated from the integrated intensity in three bands, determines 2.2 nm thickness in the shell in spherical shape of nanocrystals in 35 nm diameter.     

High-resolution infrared and theoretical study of four fundamental bands of gaseous 1,3,4-oxadiazole between 800 and 1600 cm

The Fourier transform infrared spectrum of gaseous 1,3,4-oxadiazole, C₂H₂N₂O, has been recorded in the 800–1600 cm⁻¹ wavenumber region with a resolution around 0.0030 cm⁻¹. The four fundamental bands ν₉(B₁; 852.5 cm⁻¹), ν₁₄(B₂; 1078.5 cm⁻¹), ν₄(A₁; 1092.6 cm⁻¹), and ν₂(A₁; 1534.9 cm⁻¹) are analyzed by the standard Watson model. Ground state rotational and quartic centrifugal distortion constants are obtained from a simultaneous fit of ground state combination differences from three of these bands and previous microwave transitions. Upper state spectroscopic constants are obtained for all four bands from single band fits using the Watson model. The ν₄ and ν₁₄ bands form a c-Coriolis interacting dyad, and the two bands are analyzed simultaneously by a model including first and second order Coriolis resonance using the ab initio predicted Coriolis coupling constant . An extended local resonance in ν₂ is explained as higher order b-Coriolis type resonance with ν₆ + ν₁₀, which is further perturbed globally by the ν₁₅ + ν₁₀ level. A fit of selected low-J transitions to a triad model including ν₂(A₁), ν₆ + ν₁₀(B₁), and ν₁₅ + ν₁₀(A₂) using an ab initio calculated Coriolis coupling constant is performed.The rotational constants, ground state quartic centrifugal distortion constants, anharmonic frequencies, and vibration–rotational constants (α-constants) predicted by quantum chemical calculations using a cc-pVTZ and TZ2P basis with B3LYP methodology, are compared with the present experimental data, where there is generally good agreement. A complete set of anharmonic frequencies and α-constants for all fundamental levels of the molecule is given.     

Line Positions and Intensities of the ν1+ ν2+ 3ν3, ν2+ 4ν3, and 3ν1+ 2ν2Bands of Ozone

Using a Fourier transform spectrometer, we have recorded the spectra of ozone in the region of 4600 cm⁻¹, with a resolution of 0.008 cm⁻¹. The strongest absorption in this region is due to the ν₁+ ν₂+ 3ν₃band which is in Coriolis interaction with the ν₂+ 4ν₃band. We have been able to assign more than 1700 transitions for these two bands. To correctly reproduce the calculation of energy levels, it has been necessary to introduce the (320) state which strongly perturbs the (113) and (014) states through Coriolis- and Fermi-type resonances. Seventy transitions of the 3ν₁+ 2ν₂band have also been observed. The final fit on 926 energy levels withJ_max= 50 andK_max= 16 gives RMS = 3.1 × 10⁻³cm⁻¹and provides a satisfactory agreement of calculated and observed upper levels for most of the transitions. The following values for band centers are derived: ν₀(ν₁+ ν₂+ 3ν₃) = 4658.950 cm⁻¹, ν₀(3ν₁+ 2ν₂) = 4643.821 cm⁻¹, and ν₀(ν₂+ 4ν₃) = 4632.888 cm⁻¹. Line intensities have been measured and fitted, leading to the determination of transition moment parameters for the two bands ν₁+ ν₂+ 3ν₃and ν₂+ 4ν₃. Using these parameters we have obtained the following estimations for the integrated band intensities,S_V(ν₁+ ν₂+ 3ν₃) = 8.84 × 10⁻²²,S_V(ν₂+ 4ν₃) = 1.70 × 10⁻²², andS_V(3ν₁+ 2ν₂) = 0.49 × 10⁻²²cm⁻¹/molecule cm⁻²at 296 K, which correspond to a cutoff of 10⁻²⁶cm⁻¹/molecule cm⁻².     

CW-Cavity Ring Down Spectroscopy of O3. Part 3: Analysis of the 6490–6900 cm region and overview comparison with the O3 main isotopologue

This paper is devoted to the third part of the analysis of the very weak absorption spectrum of the ¹⁸O₃ isotopologue of ozone recorded by CW-Cavity Ring Down Spectroscopy between 5930 and 6900 cm⁻¹. In the two first parts [A. Campargue, A. Liu, S. Kassi, D. Romanini, M.-R. De Backer-Barilly, A. Barbe, E. Starikova, S.A. Tashkun, Vl.G. Tyuterev, J. Mol. Spectrosc. (2009), doi: 10.1016/j.jms.2009.02.012 and E. Starikova, M.-R. De Backer-Barilly, A. Barbe, Vl.G. Tyuterev, A. Campargue, A.W.Liu, S. Kassi, J. Mol. Spectrosc. (2009) doi: 10.1016/j.jms.2009.03.013], the effective operators approach was used to model the spectrum in the 6200–6400 and 5930–6080 cm⁻¹ regions, respectively. The analysis of the whole investigated region is completed by the present investigation of the 6490–6900 cm⁻¹ upper range. Three sets of interacting states have been treated separately. The first one falls in the 6490–6700 cm⁻¹ region, where 1555 rovibrational transitions were assigned to three A-type bands: 3ν₂ + 5ν₃, 5ν₁ + ν₂ + ν₃ and 2ν₁ + 3ν₂ + 3ν₃ and one B-type band: ν₁ + 3ν₂ + 4ν₃. The corresponding line positions were reproduced with an rms deviation of 18.4 × 10⁻³ cm⁻¹ by using an effective Hamiltonian (EH) model involving eight vibrational states coupled by resonance interactions. In the highest spectral region – 6700–6900 cm⁻¹ – 389 and 183 transitions have been assigned to the ν₁ + 2ν₂ + 5ν₃ and 4ν₁ + 3ν₂ + ν₃ A-type bands, respectively. These very weak bands correspond to the most excited upper vibrational states observed so far in ozone. The line positions of the ν₁ + 2ν₂ + 5ν₃ band were reproduced with an rms deviation of 7.3 × 10⁻³ cm⁻¹ by using an EH involving the {(054), (026), (125)} interacting states. The coupling of the (431) upper state with the (502) dark state was needed to account for the observed line positions of the 4ν₁ + 3ν₂ + ν₃ band (rms = 5.7 × 10⁻³ cm⁻¹).The dipole transition moment parameters were determined for the different observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a complete line list provided as Supplementary Materials.The results of the analyses of the whole 5930–6900 cm⁻¹ spectral region were gathered and used for a comparison of the band centres to their calculated values. The agreement achieved for both ¹⁸O₃ and ¹⁶O₃ (average difference on the order of 1 cm⁻¹) indicates that the used potential energy surface provides accurate predictions up to a vibrational excitation approaching 80% of the dissociation energy. The comparison of the ¹⁸O₃ and ¹⁶O₃ band intensities is also discussed, opening a field of questions concerning the variation of the dipole moments and resonance intensity borrowing by isotopic substitution.     

High resolution FTIR spectroscopy of pentafluoroethane: perturbations in the Coriolis doublet of ν4 and ν13

The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm⁻¹. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν₄ (1200.7341 cm⁻¹) and ν₁₃ (1223.3 cm⁻¹) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν₄ (J_max = 86, K_{a max} = 50) and 2921 lines to ν₁₃ (J_max = 60, K_{a max} = 54). Effective rotational and centrifugal distortion constants were determined for ν₄, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν₁₃ band.     

High sensitivity ICLAS of H2O in the region of the second decade (11 520-12 810 cm)

The high resolution absorption spectrum of the H₂¹⁸O isotopologue of water has been recorded by Intracavity Laser Absorption Spectroscopy (ICLAS) with a sensitivity on the order of α_min ∼ 10⁻⁹ cm⁻¹. The 11 520-12 810 cm⁻¹ spectral region corresponding to the 3ν + δ decade of vibrational states, was explored with an ICLAS spectrometer based on a Ti:Sapphire laser. It allowed detecting transitions with an intensity down to 10⁻²⁷ cm/molecule which is about 100 times lower than the weaker line intensities available in the literature, in particular in the HITRAN database.The rovibrational assignment was performed on the basis of the results of variational calculations and allowed for assigning 3659 lines to the H₂¹⁶O, H₂¹⁸O, H₂¹⁷O, HD¹⁶O and HD¹⁸O species, leaving only 1.7% unassigned transitions. A line list including 1712 transitions of H₂¹⁸O has been generated and assigned leading to the determination of 692 rovibrational energy levels belonging to a total of 16 vibrational states, 386 being newly observed. A deviation on the order of 25% has been evidenced for the average intensity values given by HITRAN and the results of variational calculations. Ninety two transitions of the HD¹⁸O isotopologue could also be assigned and the corresponding upper rovibrational levels are given.     

High-resolution synchrotron far-infrared spectroscopy of acrolein: The vibrational levels below 700 cm

The far-infrared spectrum of acrolein, CH₂CHCHO, is studied in the 100–360 cm⁻¹ region using continuum radiation from a synchrotron source. The combination of a very high resolution spectrometer, a long absorption path, and a low sample pressure, yields observed line widths of less than 0.0008 cm⁻¹. Observation of the ν₁₈ (157.9 cm⁻¹), and ν₁₃ (323.8 cm⁻¹) fundamental bands, together with six hot bands in the same regions, gives information on eight low-lying vibrational states of the molecule, including the Fermi and Coriolis interactions among them. Combining the present assignments with previous data on the ν₁₂ (564.34 cm⁻¹) and ν₁₇ (593.08 cm⁻¹) fundamental bands, all ten excited vibrational levels below 700 cm⁻¹ are analyzed in terms of one 1-state fit, two 2-state fits, and one 5-state fit.     

Millimeter-Wave and High-Resolution Infrared Spectra of Monoisotopic SCSe: Equilibrium, Ground State, and ν1, mν2, and nν3 Rovibrational Parameters

The Fourier transform infrared spectrum of monoisotopic SC⁸⁰Se has been investigated in the ν₂, ν₃, 2ν₂, 2ν₃, and ν₁ regions with a resolution between 3 and 4 × 10⁻³ cm⁻¹. In addition, the millimeter-wave spectrum has been studied in the region 150 to 320 GHz, and ground and ν₂ = 1 excited state transitions have been measured. Ground state constants, B₀ = 2043.285 4(4) MHz and D₀ = 146.53(5) Hz, have been determined from a merge of millimeter-wave data and ground state combination differences spanning J values up to 77 and 143, respectively. The band centers ν₂ = 352.341 075(9) cm⁻¹ and ν₃ = 505.480 06(5)cm⁻¹ have been determined. The rovibrational parameters of numerous overtone and combination levels (ν₁ν^l2₂ν₃) = 02⁰0, 02²0, 03¹0, 03³0, 04⁰0, 04²0, 00⁰2, and 00⁰3 have been obtained from polynomial analyses whose standard deviations ranged from 0.7 to 3.5 × 10⁻⁴ cm⁻¹. The 10⁰0 level, ν_eff 1435.840 cm⁻¹, is anharmonically perturbed by the 04⁰0 level, with an avoided crossing at J = 55, and W₁₂₂₂₂ = 0.963 09(1) cm⁻¹. Transitions to both the upper (E⁺) and lower (E⁻) sublevels of the dyad were observed for 1 ≤ J′ ≤ 117 and 4 ≤ J′ ≤ 171, respectively, and the deperturbed wavenumbers ν₁ = 1435.542 76(2) and 4ν⁰₂ = 1432.725 00(3) cm⁻¹ were derived. Furthermore, a local crossing of the E⁻ and 04²0 levels involving l-type resonance was observed at J = 91.     

Laser gain by electron collisional pumping of Ar VII–V XII

Gain coefficients have been calculated for transitions of singlet levels ns–np of orbital n=4 and n=5 in magnesium-like ions with atomic numbers Z=18, 19, 20, 21, 22 and 23. Population inversions for 4p and 5p levels in these ions were also calculated, via electron collisional excitation, for electron temperature range of 93–231 eV and electron density range of 10¹⁶–10¹⁷ cm⁻³. Under these plasma conditions, the maximum gain that occurred for 4s–4p transition was at electron temperature of 231 eV and electron density of 4×10¹⁷ cm⁻³. Scaling of the maximum gain coefficients with atomic number Z and the plasma parameters is also presented.     

On the high resolution spectroscopy and intramolecular potential function of SO2

Two weak stretching bands, ν₁ + 3ν₃ and 3ν₁ + ν₃, of the sulfur dioxide molecule have been recorded at high resolution and analyzed for the first time with using a Fourier transform Bruker IFS-120 HR interferometer. About 1000 transitions with J^max. = 51, , and 900 transitions with J^max. = 53, have been assigned to the bands ν₁ + 3ν₃ and 3ν₁ + ν₃, respectively. Analysis of the recorded spectra was made using the model of isolated vibrational states. Parameters obtained from the fit reproduce the initial experimental ro-vibrational energies with the rms deviation of 0.0006 and 0.0012 cm⁻¹ for the bands, 3ν₁ + ν₃ and ν₁ + 3ν₃, respectively. The problem of determination of the intramolecular potential function of SO₂ is discussed.     

The ν1 and ν3 Bands of the OOO Isotopomer of Ozone

Using 0.002 cm⁻¹ resolution Fourier transform absorption spectra of an ¹⁷O-enriched ozone sample, an extensive analysis of the ν₃ band together with a partial identification of the ν₁ band of the ¹⁷O¹⁶O¹⁷O isotopomer of ozone has been performed for the first time. As for other C_2v-type ozone isotopomers [J.-M. Flaud and R. Bacis, Spectrochim. Acta, Part A 54, 3–16 (1998)], the (001) rotational levels are involved in a Coriolis-type resonance with the levels of the (100) vibrational state. The experimental rotational levels of the (001) and (100) vibrational states have been satisfactorily reproduced using a Hamiltonian matrix which takes into account the observed rovibrational resonances. In this way precise vibrational energies and rotational and coupling constants were deduced and the following band centers ν₀(ν₃) = 1030.0946 cm⁻¹ and ν₀(ν₁) = 1086.7490 cm⁻¹ were obtained for the ν₃ and ν₁ bands, respectively.     

Analysis of the ν3 band of NO2

The rotational structure of the ν₃ fundamental of ¹⁴N¹⁶O₂ has been recorded by employing a vacuum grating infrared spectrograph. The analysis has led to the assignment of over 500 R- and P-branch transitions in the spectral region 1562–1650 cm⁻¹. Molecular constants for the upper state, 001, have been presented. No Q-branch transitions were used in the evaluation of these constants. The presently obtained and the band center ν₀ = 1616.846 cm⁻¹ differ significantly from previous determinations. Spin splitting was observed but no information was extracted about upper state spin splitting parameters.     

The Vibrational Ground State of CHD3

Within the scope of a general tensorial study of the 1000 and 2000 cm⁻¹ polyads of CHD₃, we have revisited the ground state of this molecule. Infrared ground state combination differences (GSCD) were calculated from 1746 transitions assigned in the ν₃/ν₅/ν₆ triad of CHD₃. A set of 10 ground state parameters has been fitted to 613 GSCD providing an agreement of 0.00014 cm⁻¹ between observed and calculated transitions. This corresponds to an improvement of about one order of magnitude with respect to the previous study, reflecting the quality of the experimental spectrum as well as a strict selection of the data used to fit the parameters.     

The sub-millimeter and Fourier transform microwave spectrum of HZnCl (X Σ)

The pure rotational spectrum of HZnCl (X ¹Σ⁺) has been recorded using sub-millimeter direct-absorption methods in the range of 439–540 GHz and Fourier transform microwave (FTMW) techniques from 9 to 39 GHz. This species was produced by the reaction of zinc vapor and chlorine gas with H₂ or D₂ in a d.c. glow discharge for the sub-millimeter studies. In the FTMW measurements, HZnCl was created in a discharge nozzle from Cl₂ and (CH₃)₂Zn. Between 5 and 10 rotational transitions were measured in the sub-millimeter regime for four zinc and two chlorine isotopologues; four transitions were recorded with the FTMW machine for the main isotopologue, each consisting of several chlorine hyperfine components. The data are consistent with a linear molecule and a ¹Σ⁺ ground electronic state. Rotational and chlorine quadrupole constants were established from the spectra, as well as an r_m⁽²⁾ structure. The Zn–Cl and Zn–H bond lengths were determined to be 2.0829 and 1.5050 Å, respectively; in contrast, the Zn–Cl bond distance in ZnCl is 2.1300 Å, longer by 0.050 Å. The zinc–chlorine bond distance therefore shortens with the addition of the H atom. The ³⁵Cl electric quadrupole coupling constant of eQq = −27.429 MHz found for HZnCl suggests that this molecule is primarily an ionic species with some covalent character for the Zn–Cl bond.     

Electrical characterisation of phosphorus-doped ZnO thin films grown by pulsed laser deposition

Phosphorus-doped ZnO films were grown by pulsed laser deposition using a ZnO:P₂O₅-doped target as the phosphorus source with the aim of producing p-type ZnO material. ZnO:P layers (with phosphorus concentrations of between 0.01 to 1 wt%) were grown on a pure ZnO buffer layer. The electrical properties of the films were characterised from temperature dependent Hall-effect measurements. The samples typically showed weak n-type conduction in the dark, with a resistivity of 70 Ω cm, a Hall mobility of μ_n0.5 cm² V ⁻¹ s⁻¹ and a carrier concentration of n3×10¹⁷ cm⁻³ at room temperature. After exposure to an incandescent light source, the samples underwent a change in conduction from n- to p-type, with an increase in mobility and decrease in concentration for temperatures below 300 K.     

High-resolution FTIR spectroscopy of HNSO—Analysis of the highly perturbed ν4, ν6 and 2ν5 bands

We report a rovibrational analysis of the ν₄ and ν₆ fundamentals and the 2ν₅ overtone of HNSO from high-resolution Fourier transform infrared spectra. The ν₆ band (out-of-plane bend) centred at 757.5 cm⁻¹ is c-type. The ν₄ band (HNS bend) centred at 905.9 cm⁻¹ is predominantly a-type with a very weak b-type component (). Numerous global perturbations and localized avoided crossings affecting the v₄ = 1 rotational levels were successfully treated by inclusion of Fermi and c-axis Coriolis resonance terms between v₄ = 1 and v₅ = 2, and a b-axis Coriolis resonance term between v₄ = 1 and v₆ = 1. The latter term gives rise to an avoided crossing with an extraordinary ΔK_a = 5 selection rule. The Fermi resonance between v₄ = 1 and v₅ = 2 gives rise to strong mixing of their rotational wavefunctions in the vicinity of K_a = 18. The resultant borrowing of intensity made it possible for 2ν₅ transitions in the range K_a = 16–19 to be assigned and included in a global rovibrational treatment of all three band systems.     

Measurement and analysis of the ν4 band of silane

The ν₄ band of silane has been recorded with a resolution of about 0.06 cm⁻¹ in the region from 850 to 950 cm⁻¹. Assignments of all allowed transitions in this range with J′ ≤ 12 have been made on the basis of frequency and relative intensity. Qualitative agreement with theory is good but quantitative agreement begins to break down above J′ = 8. The breakdown is attributed to the effects of the strong Coriolis interaction with nearby ν₂.Lines of ²⁹SiH₄ and ³⁰SiH₄ have been observed in the R branch with constant isotope shifts of −1.334 cm⁻¹ and −2.600 cm⁻¹.     

The 2ν8 Band of CH3CN

The overtone band 2ν⁰₈ of CH₃CN around 720 cm⁻¹ has been measured on a Bruker Fourier transform spectrometer at a resolution of 0.003 cm⁻¹. Only the parallel band was observed, but due to the l(2, 2) resonance, ΔK = −2 lines leading to the v₈ = 2, l₈ = −2 levels with K = 1-3 could be seen. More information for the l₈ = ±2 component of the vibrational state v₈ = 2 was evaluated from the hot band 2ν^±2₈ - ν^±1₈. Altogether more than 1000 lines were assigned. In the fit pure rotational lines from literature were also combined. Among the results the anomalous A₀ - A′ values 4.6722(13) × 10⁻³ cm⁻¹ for the 2ν⁰₈ band and 7.0324(32) × 10⁻³ cm⁻¹ for the 2ν^±2₈ band are striking.     

High-resolution infrared study of the 2ν3 (A1, E) and ν1 + ν3 (E) bands of NF3

The 2ν₃ overtone (A₁, E) and the ν₁ + ν₃ (E) combination bands of the oblate symmetric top ¹⁴NF₃ were studied by FTIR spectroscopy with a resolution of 2.5 × 10⁻³ cm⁻¹. Nearly 500 lines up to K_max/J_max = 30/43 were observed for the weak A₁ component reaching the v₃ = 2⁰ substate (1803.1302 cm⁻¹), the majority of which corresponded to reinforced K = 3p-type transitions. For the strong E component reaching the v₃ = 2^±2 substate (1810.4239 cm⁻¹), about 3550 transitions were assigned up to K_max/J_max = 65/69, favoring a clear observation of the ℓ(4, −2) and ℓ(4, 4) splittings within the kℓ = −2 and +4 sublevels, respectively. The two v₃ = 2 substates are linked by the ℓ(2, 2)- and ℓ(2, −1)-type interactions, providing severe crossings, respectively, at K′ = 6 and near K′ = 24 on the v₃ = 2⁺² side. A model working in the D-reduction and including all these ℓ-type interactions could reproduce together 3695 nonzero weighted experimental data (NZW) through 33 free parameters with a standard deviation of σ = 0.357 × 10⁻³  cm⁻¹. As for the ν₁ + ν₃ (E) combination band, about 3690 lines were assigned up to K_max/J_max = 45/55. Its v₁ = v₃ = 1 upper state (1931.577 5 cm⁻¹) was treated using the same model recently applied to the v₃ = 1 (E, 907.5413 cm⁻¹) state. It yielded 21 free parameters through 3282 NZW experimental data, adjusted with σ = 0.344 × 10⁻³  cm⁻¹ in the D-reduction. For the two excited states, the small and unobserved ℓ(0, 6) interaction was tested as useless. To confirm the adequacy of the vibrationally isolated models used, some other reductions of the Hamiltonian were tried. For the v₃ = 2 state, the D-, L-, and LD-reductions led to similar σ’s, while the Q one was not successful. For the v₁ = v₃ = 1 state, the D- and Q-reductions gave comparable σ’s, while the QD-reduction was not as good. The corresponding unitary equivalence relations are generally more nicely fulfilled for the v₃ = 2 state than for the v₁ = v₃ = 1 state. The three derivable anharmonicity constants in cm⁻¹ are x₃₃ = −4.1528, g₃₃ = +1.8235 and x₁₃ = −7.9652.