The infrared spectrum of DCCF in the 320–850 cm−1 region: bending states up to υ4+υ5 = 3

Infrared spectra of deuterated monofluoroacetylene, DCCF, have been recorded in the region between 320 and 850 cm^?1 at an effective resolution ranging from 0.0024 to 0.0031 cm^?1. In total, 6650 rotation vibration transitions were assigned to 37 bands involving the bending states with v₄ + v₅ and |l₄+l₅|, respectively, up to 3, allowing the characterisation of the ground state and of 18 vibrationally excited states. The vν₅ bending fundamental has been studied for the first time. In addition, the difference band v₃ ← v₄ has been detected and analysed. All the assigned transitions have been fitted simultaneously by adopting a model Hamiltonian that takes into account the vibration and rotation l?type resonances. Rotational transitions in the ground and in bending excited states reported in the literature have been included in the global analysis. The set of 57 derived spectroscopic parameters reproduces 6130 infrared and 90 microwave and millimetre?wave transitions satisfactorily with root mean square values of 5.3 × 10^?4 cm^?1 and 77 kHz, respectively.     

The region of the 3ν3 band of methane

The spectrum of methane near 9000 cm^?1, the region of the 3ν₃ band, has been recorded at Meudon Observatory with a Fourier transform spectrometer under high resolution. Intensity measurements at two different temperatures, 149 and 295 K, have allowed us to identify two new vibration bands by determining the lower-state quantum numbers J of the transitions. About 100 lines are now assigned in this range, including P and Q branches. Furthermore, the first detailed rotational analysis of the 3ν₃ band has been made; nine parameters of the band have been determined. The standard deviation of the differences between observed and computed wavenumbers for 45 lines of the 3ν₃ band is only 0.045 cm^?1. It is found that the observed 45 lines of the 3ν₃ band correspond to the sublevel l₃ = 3 and C_v = F₂.     

Analysis of the ν6 band of 12CH3D at 8.6 μm

The ν₆(E) fundamental vibration-rotation band of monodeuteromethane (¹²CH₃D) has been recorded in the spectral range 1033–1270 cm^?1 with a resolution of approximately 0.04 cm^?1. Of the 669 transitions with J′ ≤ 17 identified, 633 have been retained for the determination of the rotational levels in the upper state v₆ = 1. The Coriolis interaction between the v₆ = 1(E) and v₃ = 1 (A₁) vibrational states of ¹²CH₃D results in large A₁A₂ splittings of levels with v₆ = 1 and |K ? l₆| = 0 or 3; the mixing in K and l₆ also gives rise to some ten forbidden transitions observed in the spectra. These effects have been very well explained within the formulation based on the contact transformation method. Values of 15 molecular structure constants of the v₆ = 1 state have been determined from a least-squares analysis of the 633 retained transitions. These constants can be used to estimate values of the upper-state energies up to fourth order, and through them the spectral positions of the 633 retained transitions are reproduced with an overall standard deviation of 0.013 cm^?1, which is within experimental uncertainties.     

High-resolution spectroscopy of the v2 = 2 a ← v2 = 1 s band of 15NH3

Twenty-four transitions of the v₂ = 2 a ← v₂ = 1 s hot band of ¹⁵NH₃ have been observed by an infrared microwave sideband laser spectrometer. In addition, 149 transitions of the band have been obtained by a Fourier transform spectrometer at a resolution of 0.02 cm⁻¹. A weighted least-squares analysis has been carried out and the rms deviation of the fit is 0.00097 cm⁻¹. It was necessary to include the Δ(K − l) = ±3 interaction between the v₂ = 2 a and the v₄ = a states in the analysis.     

High-resolution FTIR spectroscopy of CHD279Br: ro-vibrational analysis of the v4 fundamental and determination of the ground state constants

The first high-resolution infrared spectrum of CHD₂⁷⁹Br has been investigated by Fourier transform spectroscopy in the range 940–1100 cm^?1 at an unapodised resolution of 0.0025 cm^?1. This spectral region is characterised by the v₄ (1036.8389 cm^?1) fundamental band, corresponding to the CD₂ wagging mode. The rotational structure of the a- and c-type components of the hybrid band has been extensively assigned for transitions involving values of J and K_a up to 65 and 15, respectively. The ground state constants up to the quartic centrifugal distortion terms have been obtained for the first time by ground state combination differences from 5251 assigned transitions and subsequently employed for the evaluation of the band origin and the excited state parameters of v₄. Watson’s S-reduced Hamiltonian in the I^r representation has been used in the ro-vibrational analysis. The dipole moment ratio |Δμ_a/Δμ_c| of the band has been estimated to be 1.3?±?0.1 from spectral simulations.     

Prebreakdown excitation of crystals at double multiphoton resonance: I. Probabilities of interband transitions

Expressions for the probabilities of l-photon transitions (for arbitrary l) between the upper valence band v and lower conduction band c at two-photon resonance on the adjacent transition between the band c and the upper conduction band c ₁ are obtained by means of the S transformation of the electron-photon Hamiltonian. The effects of electron band spectrum transformation and photon reemission are taken into account.     

Analysis of phosphine absorption in the region 9–10 μm and high-resolution line-by-line simulation of the ν2 and ν4 bands

Phosphine absorption is analyzed in the range 818–1340 cm^?1 from laboratory spectra recorded at Denver University with a resolution of 0.05 cm^?1. A refined treatment of the Coriolis interaction between ν₂ and ν₄ is introduced, allowing interpretation of the rotational structure of the two bands up to high J′ values, including the large observed A₁A₂ splittings. A fit, based on 1187 experimental transitions, leads to a set of spectroscopic constants applicable to a high-resolution, line-by-line simulation of the two bands ν₂ and ν₄. The overall standard deviation of the fit is 0.017 cm^?1. About 70 transitions belonging to the “hot” band 2ν₂-ν₂ are also identified, consistent with a band center near 980.4 cm^?1.     

High-resolution spectroscopy of the v2 = 2 a ← v2 = 1 s band of 14NH3

Twenty-one transitions of the v₂ = 2 a ← v₂ = 1 s hot band of ¹⁴NH₃ have been observed by an infrared microwave sideband laser spectrometer with an absolute accuracy of 0.00002 cm⁻¹. One hundred and seventeen transitions of the band have been obtained by a Fourier transform infrared spectrometer at a resolution of 0.005 cm⁻¹. A weighted least-squares analysis of these data has been carried out to yield 17 molecular parameters for the v₂ = 2 a state. These parameters reproduce the experimental frequencies with a root mean square deviation of 0.000123 cm⁻¹. To calculate the frequencies to this accuracy it was necessary to take into account the Δ(K − l) = ±3 interaction between the v₂ = 2 a and v₄ = 1 a states.     

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

The overtone band 2ν₆ of ¹²CH₃D 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 A₁A₂ splittings. Six hundred twelve transitions including J′ values up to 13 are assigned; the vibration-rotation constants for the upper state v₆ = 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 2ν₆.     

Diode laser spectrum of HCCl near 5 μm: The ν2 fundamental and accompanying hot bands

The CC stretching band ν₂ of iodoacetylene has been studied by tunable laser spectroscopy in the range of 2037–2071 cm^?1. The hot bands associated with the low-lying bending vibrations ν₄ and ν₅ were observed. For the Π-Π hot bands, the splitting caused l-type doubling was resolved for high J transitions. For the fundamental band the hyperfine splittings due to the ¹²⁷I nuclear quadrupole moment were clearly observed for R(0) and P(1) transitions. Combination of these diode laser spectra with the microwave data allows precise determination of the constants in the ground and excited vibrational states.     

The ν1, ν2, and ν3 Band Systems of 3-Isocyano-2-propynenitrile (NCCCNC): Comparison with the ν4 System of Dicyanoacetylene

The hot bands in the ν₁, ν₂, and ν₃ band systems of NC-CC-NC (3-isocyano-2-propynenitrile) have been investigated and transitions from nv₉-levels with n up to 4 have been identified. Two weak bands have also been observed in the gas phase infrared spectrum at 2157 and 2410 cm⁻¹, of which the latter is probably 2v₄. A preliminary investigation of some analogous hot bands in the v₄ band system of the related molecule NC-CC-CN (dicyanoacetylene) is also reported.     

Absorption spectrum of trideuteromethane between 7 and 11 μm. Analysis of the ν5 band

The absorption spectrum of trideuteromethane was recorded in the range 900–1400 cm^?1 with a resolution of 0.020–0.025 cm^?1. The ν₅ band centered at 1292.499 cm^?1 is analyzed here. A fit based on 869 observed transitions including J′ values up to 22, leads to a set of spectroscopic constants suitable for energy calculations in the upper-state v₅ = 1. These constants reproduce the experimental wavenumbers with a standard deviation equal to 0.008 cm^?1. The tabulated line strengths are calculated on the basis of the value S = 27.1 cm^?2 atm^?1 at 300 K, measured by Hiller and Straley, for the band strength of ν₅. A useful comparison is made between the values now derived for some constants and the corresponding ones predicted by Gray and Robiette in their recent force field calculations of methane and isotopic species.     

The infrared spectrum of C3O2: The interaction between ν7 and the ν2 and ν4 vibrations

The 3ν¹₇, 3ν³₇, and 4ν⁰₇ hot bands of the ν₄ fundamental of C₃O₂ in the 1580 cm^?1 region were analyzed from tunable diode laser spectra and the ground state to ν₄ + 2ν⁰₇ band at 1644 cm^?1 from Fourier transform spectra (FTS). The molecular constants for all of the v₄ 1 ← 0 bands as well as the intensity of the ν₀ + 2ν⁰₇ sum band relative to the ν₄ fundamental were in agreement with the predictions of the model of Weber and Ford. FTS spectra at 0.05 cm^?1 resolution were obtained of the sum and difference bands of ν₂ with ν₇ in the 750–900 cm^?1 region. Sharp Q branches occur for each ν₇ state in the sum bands, but only a number of R-branch bandheads and no recognizable Q branches in the difference bands. Assignments of the sum band Q branches through v₇ = 6 were made and molecular constants were determined for the ν₂ + ν¹₇ ← 0 transition at 819.7 cm^?1. The ν₇ potential function in the v₂ = 1 state was found to have a 1.2 cm^?1 barrier with a minimum at α = 4.9°, where 2α is the angular deviation from linearity. The Q-branch positions predicted from the calculated energy levels fit those observed within several cm^?1.     

The ν2 and ν4 bands of AsH3

The infrared absorption of arsine, AsH₃, between 750 and 1200 cm^?1 has been recorded at a resolution of 0.006 cm^?1. Altogether 2419 transitions, including nearly 700 “perturbation allowed” transitions with Δ∥k ? l∥ = ±3, ±6, and ±9, have been assigned to the ν₂(A₁) and ν₄(E) bands. Splitting of the transitions for K″ = 3, 6, and 9 was also observed. To fit the rotational pattern of the v₂ = 1 and v₄ = 1 vibrational states up to J = 21, all the experimental data were analyzed simultaneously on the basis of a rovibrational Hamiltonian which took into account the Coriolis interaction between ν₂ and ν₄ and also included several essential resonances within them. The derived set of 38 significant spectroscopic parameters reproduced the 2328 transition wavenumbers retained in the final fit within the accuracy of the experimental measurements.     

Analysis of the ν3 band of 12CH3D at 7.6 μm

The previously reported (J. Mol. Spectrosc.68, 195–222 (1977)) study of the CH₃D spectrum occurring at 1033–1270 cm^?1 which was mainly concerned with the ν₆ fundamental has now been extended to cover the region 1270–1420 cm^?1. In all, 342 transitions belonging to the ν₃ band are now assigned. Both the ν₃ and ν₆ bands are processed simultaneously taking into account of the Coriolis interaction between them, and the fitting of all the experimental data led to 21 significant spectroscopic constants for the states v₆= 1 and v₃ = 1 of CH₃D.     

High resolution FTIR spectroscopy of CH2DF: analysis of the v 3 and v 4 interacting bands

The high resolution (0.004cm^?1) Fourier transform infrared spectrum of the monodeuterated form of methyl fluoride, CH₂DF, has been recorded and analysed in the v ₃ and v ₄ band region around 1420cm^?1. Both bands, coming from A′ symmetry vibrations, have a/b hybrid character, although in v ₃ the b-type component prevails over the a-type. The rotational structure has been analysed using a dyad model including c-type Coriolis coupling and high order vibrational resonance between these states. Accurate upper state molecular parameters and interaction terms have been obtained by fitting about 3270 assigned transitions to Watson's A-reduced Hamiltonian in the I^r representation. In addition, from a simultaneous fit of ground state combination differences coming from this analysis and 42 literature microwave transitions, an improved and more complete set of ground state constants, including three new sextic centrifugal distortion terms (Φ_JK, Φ_KJ and Φ_K), has been derived.     

The bending-rotation spectrum of fulminic acid and deuterofulminic acid

A quasilinear molecular model is needed to account for the infrared absorption spectrum of HCNO and DCNO in the spectral region from 100 cm^?1 to 1000 cm^?1. The observed systems of infrared bands arising from the ν₅ vibrational manifold have all been assigned. The rotational structure of the absorption bands at 225 cm^?1, 275 cm^?1, 315 cm^?1, and 317 cm^?1 for HCNO has been resolved using a Fourier spectrometer. The rotational constants and the band centers have been determined for the above bands, which represent the transitions(0000⁰1¹)_c←0000⁰0⁰(0000⁰2²)_c,d←(0000⁰1¹)_c,dboth components(0000⁰3³)_c,d←(0000⁰2²)_c,d0000⁰2⁰←(0000⁰1¹)_c.By means of the Ritz combination principle the infrared transitions could be used to build up the vibrational energy level scheme of the ν₅ vibrational mode for HCNO and DCNO. The data are only reconcilable with a potential function for ν₅ which exhibits a low barrier opposing linearity. Preliminary values of the potential parameters were obtained using different approximate theoretical approaches.A reinterpretation of the r₈ structure parameters of fulminic acid in the light of the quasilinear model leads to an explanation of the extraordinarily short CH internuclear distance of 1.027 Å as the projection of a CH bond length of 1.060(5) Å upon the heavy-atom axis.The isotopic shift upon deuteration observed in the infrared data indicate that the ν₅ fundamental vibration is primarily an HCN bending motion. The ν₄ fundamental vibration (skeletal bending motion) of HCNO is located at 537 cm^?1 and does not exhibit any hot band structure which would be indicative of a perturbed potential function.     

Analysis of the ν2 and ν4 infrared bands of CD4

The infrared spectrum of totally deuterated methane CD₄ has been recorded between 930 cm^?1 and 1180 cm^?1 under high resolution (0.003 cm^?1). The ν₂ and ν₄ bands of ¹²CD₄ have been reanalyzed on the basis of a complete third-order Hamiltonian including all the coupling terms linking the upper states of the two bands. A set of only 16 self-consistent parameters have been adjusted to fit more than 1650 assigned transitions reaching a maximum upper state J value of 20. The obtained standard deviation is 0.0041 cm^?1. In addition, 171 lines of the ν₄ band of ¹³CD₄ have been assigned. They have been analyzed, in the same dyad scheme, by adjusting 7 parameters of the ν₄ band together with the main ζ₂₄ Coriolis parameter. The obtained standard deviation is only 0.0012 cm^?1.     

Absorption spectrum of trideuteromethane between 8 and 11.5 μm: Analysis of the ν3 and ν6 bands

The analysis of the absorption spectrum of ¹²CD₃H, previously reported for the region 1200–1400 cm^?1 concerned with the ν₅ band, is now extended to cover the region 872–1213 cm^?1 including the two bands ν₃ and ν₆. These are centered at 1004.553 and 1035.917 cm^?1, respectively, and strongly coupled by a Coriolis interaction. A formulation taking this interaction into account rigorously was used; as a result, the energies for the upper states v₃ = 1 and v₆ = 1 are derived as eigenvalues of an effective Hamiltonian

(J. Mol. Spectrosc.79, 31–46 (1980)). The fit of the upper-state constants based on 1434 observed transitions including J′ and K′ values up to 22 leads to a set of 22 significant values which reproduce the observed wavenumbers with a standard deviation of 0.007 cm^?1 close to the experimental uncertainties.     

New measurements and global analysis of chloromethane in the region from 0 to 1800 cm

New high resolution Fourier transform spectra of pure ¹²CH₃³⁵Cl and ¹²CH₃³⁷Cl isotopomers of chloromethane have been recorded in Wuppertal covering the region from 600 to 3800 cm⁻¹. New rotational transitions within the v₂=1, v₅=1, and v₃=2 states have been measured at Lille. A first global analysis of the lower four band systems of the molecule (700-1800 cm⁻¹) is reported. The model was based on an effective Hamiltonian and dipole moment expressed in terms of irreducible tensor operators. A common set of 125 effective hamiltonian parameters (sixth order) has been adjusted to fit simultaneously some 11 000 IR data for each of the isotopomers including 153 mm wave data for 12CH₃35Cl. The assignments involve 12 sets of transitions (6 cold bands, 3 hot bands, and 3 pure rotational systems for ¹²CH₃³⁵Cl). The standard deviation was on average 0.00014 cm⁻¹ and 175 kHz for the IR and MMW data, respectively. The v₃=v₆=1 state was analysed for the first time principally from observed hot band transitions.