A. Valentin

Analysis of high resolution fourier transform and diode laser spectra of the ν9 band of ethane

Abstract Fourier transform measurements with an apodized apparatus function up to 0.002 cm−1 are reported for the ν9 band (ρu) of ethane in the 12-μm region, together with an integrated band strength obtained from intensity measurements on selected Q-branch lines recorded using a diode laser spectrometer. Since the ν9 band falls in an atmospheric window, these data may be useful in studies of the ethane concentration in the atmosphere of Jupiter and other outer planets. Torsional splittings in the ν9 level caused by a higher-order Coriolis interaction with the close lying 3ν4 state (a1u) have been analyzed in a global least squares fit of 2206 Fourier transform lines and 58 diode splittings to a molecular Hamiltonian containing 20 parameters, with a standard deviation of 0.35 × 10−3 cm−1. Rotational levels of one component of the torsionally split 3ν4 state cross interacting rotational levels of the ν9 state for K = 17, and the spectrum is followed to K = 19 on the pP subband side to permit inclusion of ν9 levels beyond this crossing. No transitions to 3ν4 levels were observed. The theoretical treatment presented here makes use of standard symmetric top formalism and of the G 36 † double-group formalism for ethane.

Extension to third-order Coriolis terms of the analysis of ν10, ν7, and ν4 levels of ethylene on the basis of Fourier transform and diode laser spectra

Abstract The ν 7 , ν 10 , and ν 4 levels of ethylene have been studied based on waveguide laser, Fourier transform, and diode laser spectra in the range from 798 to 1091 cm −1 . The absolute calibration of these spectra is better than 0.0002 cm −1 . To deal with so many and so accurate experimental data, we have developed in our analysis programs the Watson Hamiltonian up to the sextic centrifugal distortion coefficients and the interaction Hamiltonian up to the third-order Coriolis resonance terms. The molecular parameters of the vibrational ground state have been significantly improved on the basis of more than 4000 GSCD. In the analysis of ν 7 , ν 10 , and ν 4 levels, we had to introduce the ν 12 level, which contributes to the indirect coupling of ν 7 and ν 4 through strong Coriolis interactions. We obtain a statistical agreement with all experimental data with an estimated standard deviation equal to 0.84. The intrinsic intensity of the ν 10 band has been determined to be 16 500 ± 2500 times lower than the intensity of the ν 7 band.

The ν2 band of 15NH3

Abstract High-resolution Fourier transform sepctra of the ν 2 band of 15 NH 3 have been recorded in the region 725–1250 cm −1 with a precision better than 0.0003 cm −1 . A simultaneous weighted least-squares analysis of these data, together with previously published data, has been carried out, to yield molecular parameters which fit the data within the limits of their experimental accuracies.

Absorption of monodeuteromethane 12CH3D at 4.5 μM, analysis of the overtone band 2ν6

Abstract The overtone band 2 ν 6 of 12 CH 3 D is analyzed in the range 2088–2433 cm −1 . The parallel and perpendicular components, centered at 2316.266 and 2323.297 cm −1 , are strongly interacting, giving rise to a number of “forbidden” transitions and large A 1 A 2 splittings. Six hundred twelve transitions including J ′ values up to 13 are assigned; the vibration-rotation constants for the upper state v 6 = 2 are derived from these data, allowing the reproduction of the experimental wavenumbers with a rms equal to 0.007 cm −1 . Some intensity measurements are used to estimate the overall band strength of 2 ν 6 .

Analysis of the absorption spectrum of 12CD4 between 2180 and 2320 cm−1. Comparative study of ν3 and 2ν3

Abstract The high-resolution spectrum of the ν3 band of 12CD4 has been recorded and analyzed. Corresponding to 367 allowed transitions of this band, 218 lines have been identified between 2180 and 2320 cm−1. Twelve significant spectral constants have been determined in such a way as to reproduce the spectrum with a standard deviation equal to 7 × 10−3 cm−1. A comparative analysis between the present results on ν3 and those obtained by K. Fox [J. Mol. Spectrosc. 9, 381 (1962)] for 2ν3 showed that the interaction between the two sub-levels E and F2 of the v3 = 2 state produces a significant effect of the second order and enabled us to determine the interval between these sublevels, i.e., 20 T33 ∼ 30 cm−1.

Amino wagging and inversion in hydrazine: K'=1 levels in the first excited state of the antisymmetric wagging vibration

Abstract The infrared absorption spectrum of NH 2 NH 2 vapor has been observed in the region 899–1077 cm −1 , where the antisymmetric wagging band ( v a = 1 ← 0) appears, by the use of a Fourier transform spectrometer with a practical resolution of 0.003 cm −1 . In the region 925.0–925.6 cm −1 , the spectrum was also observed with a tunable diode laser, and a component, β, of the p Q 2 cluster has been further resolved. Most of the absorption lines assignable to β - p P 2 ( J ″), γ - p P 2 ( J ″), β - p Q 2 ( J ″), γ - r Q 0 ( J ″), β - r R 0 ( J ″), and γ - r R 0 ( J ″), where J ″ = 2 ∼ 15, have been identified. From these observed transition frequencies, in combination with the ground state energy levels given by microwave spectroscopy, the energy level structure of the K ′ = 1 rotational states was determined. From this, the following molecular parameters for the v a = 1 state were determined: molecular asymmetry, B ′- C ″ = 0.00017 cm −1 ; a parameter q 5 describing an umbrella motion Coriolis interaction ( q 5 K ) about the a axis, q 5 = −0.0030 cm −1 ; its J ( J + 1) variation, q 5 j = 0.00014 cm −1 ; and a parameter describing an umbrella-motion K -type doubling g 5 J ( J + 1), g 5 = 0.000021 cm −1 .

High-resolution Fourier transform spectra and rotational analysis of monoisotopic H374Ge35Cl and H374Ge37Cl in the ν2/ν5/2ν3 region near 850 cm−1

Abstract The gas phase infrared spectra of the monoisotopic germyl chloride species H374Ge35Cl (7435) and H374Ge37Cl (7437) in the ν2/ν5/2ν3 region near 850 cm−1 have been studied with a resolution (fwhm) of ca. 0.002 cm−1 employing a Fourier transform spectrometer. A total of 4628 and 3461 transitions of (7435) and (7437), respectively, have been assigned with Kmax = 15 and Jmax = 80 for ν2(a1) and ν5(e). For 2ν3 of (7435), Kmax and Jmax were 6 and 61, respectively. Precise J-dependent ground state constants up to sextic coefficients have been determined from a fit (σ ⋍ 1.3 × 10−4 cm−1) of 1635 and 751 combination differences for (7435) and (7437), respectively. One pair of excited state levels split by Δl = ±1, Δ k = ⊣2 interactions has been observed, and A0 (in connection with DK0 determined previously) of (7437) has been obtained from the related normal and perturbation-allowed transitions. Strong Coriolis interaction, |ζ 2,5 i | ⋍ 0.65 , i = x, y, with positive intensity perturbation occurs between ν2(a1) and ν5(e). For (7437), the perturbation by 2ν3(A1) is local and restricted to the (kl) = −8 sublevels of ν5. In contrast, ν2 and 2ν3 are sufficiently close in (7435) that extended Fermi interactions, |W233F| = 1.27 cm−1, negative intensity perturbation, become dominant. The observed transitions have been fitted, σ ⋍ 1.3 × 10−4 cm−1, to excited state parameters, and a model taking into account Fermi, Δl = Δk = ±1, Δl = Δk = ±2 and Δl = ±1, Δ k = ⊣2 interactions has been employed. The following rounded vibrational frequencies ( 7435 7437 ) have been determined: ν20, 847.650 847.456 , ν50, 873.844 873.833 , and 2ν30, 843.070 827.607 cm −1 .

Rotational constants of C2D6 in the ground and v4=1 vibrational states

Abstract A high-resolution Fourier transform infrared spectrum of C 2 D 6 , in the region of the ν 6 and ν 8 fundamental vibration-rotation bands, has been partially analyzed, and the wavenumbers of the assigned transitions of the ν 8 and ( ν 4 + ν 8 ) − ν 4 bands have been used to determine the rotational parameters B , D JK , and D J of the ground and v 4 = 1 vibrational states. The observation of additional transitions, made detectable by the effect of locally resonant level couplings, allows the establishment of relations between the values of the rotational constants A and D K in the mentioned vibrational states. It is found that the available values of the quartic centrifugal distortion parameters, including D K , determined by a harmonic force field, are highly reliable; therefore accurate values of A 0 and A 4 can be evaluated.

The high-resolution Fourier transform spectrum of monoisotopic H370Ge35Cl near 850 cm−1 and rovibrational analysis of the ν2/ν5/2ν3 band with almost perfect degeneracy of ν2 and 2ν3

Abstract The FT infrared spectrum of monoisotopic H370Ge35Cl has been recorded in the ν2, ν5, 2ν3 region near 850 cm−1 with a resolution (FWHM) of 0.0024 cm−1. A rovibrational analysis has been performed, and Fermi resonance, W F ⋍ 1.19 cm −1 , between ν2, ν0 = 848.032 cm−1, and 2ν3, ν0 = 850.666 cm−1, has been established. Due to opposite signs of their αA values, ν2 and 2ν3 exhibit a K-level crossing at K = 14, and pairs of ν2, 2ν3 transitions were observed for many K values. Interaction according to Δl = Δk = ±1 (Coriolis) and Δl = ±1, Δk = ∓2 (α resonance) mechanisms of ν5, ν0 = 874.188 cm−1, with both ν2 and 2ν3 have been verified. The major contribution to the interactions involving 2ν3 is transmitted indirectly from ν2 via the Fermi term, but additional counteracting direct terms, W 335 ⋍ −2.3 × 10 −3 and W 335 α ⋍ −3.2 × 10 −6 cm −1 , were found to be of significance. The J-dependent ground state parameters were determined from 1568 ground state combination differences, while A0 = 2.632418(9) cm−1 was calculated from perturbation-allowed transitions associated with the α resonance. A total of 5357 measured transition wavenumbers were fitted to excited state parameters, σ ⋍ 1.5 × 10 −4 cm −1 , employing a truncated chain model.

The high-resolution Fourier transform infrared spectrum of H374Ge35Cl from 2000 to 2250 cm−1

Abstract The infrared spectrum from 2000 to 2250 cm−1 of monoisotopic H374Ge35Cl has been reinvestigated with a resolution (FWHM) of ca. 0.0030 cm−1. Remarkable improvements have been achieved with respect to previous rovibrational investigations employing spectra with lower resolution. The assignments of the ν1 fundamental have been extended, especially in the perturbed subbranches with 4 ≦ K ≦ 7, and the related transitions have been fitted with a standard deviation σ = 1.33 × 10−3 cm−1. The analysis of the local perturbations observed in almost all KΔK branches of ν4, according to the proposed interaction model, has led to the identification of 37 vibrotational transitions belonging to combination and overtone vibrational levels which are enhanced near resonance by intensity stealing from ν4 transitions. The fit of these 37 lines (σ = 5.72 × 10−3 cm−1) and of 565 transitions of ν4 (σ = 3.36 × 10−3 cm−1) including the resolved RQ0 lines, the corresponding RR0 lines, and those lines of the locally perturbed regions which were disregarded in the previous analyses has allowed the determination of vibration-rotation parameters of 3ν3 + ν5, ν2 + ν3 + ν5, and 2ν2 + ν3, of the vibrational wavenumbers of ν3 + 2ν5(A1), ν3 + 2ν5(E), ν2 + 3ν3, and 5ν3, and of several interaction constants. The resolution of numerous RQ0 lines of ν4 has enabled an improved determination of the l-doubling constant F4.