The infrared spectrum of 12C2HD: the bending states up to υ4 +υ5 =3

The infrared spectrum of ¹²C₂HD has been recorded at high resolution between 450 and 2100?cm^?1 by Fourier transform spectroscopy. The ν₄ and ν₅ bending fundamental bands together with overtones, combination bands and associated hot bands involving modes up to υ_tot?=?υ₄?+?υ₅?=?3 have been identified. Altogether, 43 vibrational bands have been analysed, leading to the spectroscopic characterization of the ground state and of 18 vibrationally excited states. They include all the components of the vibrational manifolds up to υ_tot?=?3, with the exception of the υ₄?=?3, ??=?±3 state. A simultaneous fit of all the assigned transitions has been performed. The adopted model includes vibration and rotation ?-type interaction resonances. The determined spectroscopic parameters reproduce the assigned wavenumber transitions with RMS values close to the estimated experimental uncertainties.     

The infrared spectrum of 13C2H2 in the 60–2600 cm−1 region: bending states up to v 4 + v 5 = 4

The vibration–rotation spectra of ¹³C substituted acetylene, ¹³C₂H₂, have been recorded in the region between 60 and 2600?cm^?1 at an effective resolution ranging from 0.001 to 0.006?cm^?1. Three different instruments were used to collect the experimental data in the extended spectral interval investigated. In total 9529 rotation vibration transitions have been assigned to 101 bands involving the bending states up to v _tot?=?v ₄?+?v ₅?=?4, allowing the characterization of the ground state and of 33 vibrationally excited states. All the bands involving states up to v _tot?=?3 have been analyzed simultaneously by adopting a model Hamiltonian which takes into account the vibration and rotation l-type resonances. The derived spectroscopic parameters reproduce the transition wavenumbers with a RMS value of the order of the experimental uncertainty. Using the same model, larger discrepancies between observed and calculated values have been obtained for transitions involving states with v _tot?=?4. These could be satisfactorily reproduced only by adopting a set of effective constants for each vibrational manifold, in addition to the previously determined parameters, which were constrained in the analysis.     

The infrared spectrum of 13C2HD between 100 and 2100 cm−1: a global fit for the bending states up to υ 4 + υ 5 = 3

The fundamental bending ro-vibrational bands and a number of overtone, combination and hot bands of ¹³C₂HD have been recorded by Fourier transform infrared spectroscopy in the range 450–2100 cm^?1. In addition, the ν ₅ ← ν ₄ band, centred at 164.65 cm^?1, has been identified in the spectrum of ¹³C₂H₂. The data were analysed simultaneously in a global fit that has provided very accurate rotational and vibrational parameters for the ground and vibrationally excited states.     

The infrared spectrum of 12C2HD: the stretching–bending combination bands in the 1800–4700 cm−1 region

The infrared spectrum of ¹²C₂HD has been observed between 1800 and 4700?cm^?1 by Fourier transform spectroscopy. The ν₁, ν₂ and ν₃ absorption bands and the associated hot and combination bands involving the bending modes up to υ_t?=?υ₄?+?υ₅?=?2 have been investigated. Altogether, 60 vibrational bands were analysed, leading to the spectroscopic characterization of 31 vibrationally excited states. Several perturbations have been observed, but the transitions involving the perturbing states have not been detected. As a consequence, an appropriate treatment of the vibrational or ro-vibrational interactions has not been possible. A tentative assignment of the perturbing states has been proposed. Eventually, global fits for each fundamental vibration and its associated cold and hot bands have been performed.     

The high-resolution infrared spectrum of ethylene in the 1800–2350 cm−1 spectral region

Fourier transform spectra of ethylene (C₂H₄) have been recorded in the 1800–2350?cm^?1 (4.3–5.6?µm) spectral region using a Bruker IFS125HR spectrometer at a resolution of 0.004?cm^?1 leading to the observation of six vibrational bands, ν ₇?+?ν ₈, ν ₄?+?ν ₈, ν ₆?+?ν ₁₀, ν ₆?+?ν ₇, ν ₄?+?ν ₆ and ν ₃?+?ν ₁₀. The corresponding upper state ro-vibrational levels were fit using a Hamiltonian matrix accounting for numerous interactions. A satisfactory fit could be obtained using a polyad of nine interacting states {8¹10¹,?7¹8¹,?4¹8¹,?8¹12¹,?6¹10¹,?6¹7¹,?4¹6¹,?3¹10¹,?3¹7¹} of which three (8¹10¹, 8¹12¹ and 3¹7¹) are unobserved dark states. As a result a much more accurate and extended set of Hamiltonian constants were obtained than previously derived. The following band centers were determined: ν ₀(ν ₇?+?ν ₈)?=?1888.9783(20)?cm^?1, ν ₀(ν ₄?+?ν ₈)?=?1958.2850(20)?cm^?1, ν ₀(ν ₆?+?ν ₁₀)?=?2047.7589(20)?cm^?1, ν ₀(ν ₆?+?ν ₇)?=?2178.011(60)?cm^?1, ν ₀(ν ₄?+?ν ₆)?=?2252.8026(24)?cm^?1 and ν ₀(ν ₃?+?ν ₁₀)?=?2171.2397(20)?cm^?1. Finally, a synthetic spectrum that could be useful for ethylene detection in planetary atmospheres was generated.     

Analysis of the Fourier transform infrared spectrum of the stannane species 116SnH4 in the region 1270–1600 cm-1

Monoisotopic stannane 116SnH4 has been investigated at room temperature in the 600–850 cm-1 and 1270–1600 cm-1 regions by FTIR spectroscopy with an effective resolution of 2.1 ×10-3 cm-1 and 2.0 ×10-3 cm-1 respectively. The simultaneous analysis of infrared transitions of both the bending triad and the hot band {bending triad} minus {bending dyad}, enabled us to determine 26 parameters for the (22) band and the combination band (2+4). The standard deviation of the fit was about 1.5×10-3 cm-1. In this analysis, we have used, for the bending triad, a Hamiltonian developed to the fourth order of approximation. 163 observed transitions for the hot band and most observed transitions for the bending triad spectrum, were assigned to the two bands 22 and (2+4), up to J=9. In the fit of the Hamiltonian parameters, we have used for the ground state and for the fundamentals 2 and 4, the parameters determined by Brunet, Pierre, and Bürger [J. Mol. Spectrosc. 140, 237 (1990)].     

The absorption spectrum of 12C2D2 in the 10000–12500 cm−1 spectral region

The absorption spectrum of dideuteroacetylene has been recorded by intracavity laser absorption spectroscopy (ICLAS) in the 10 200–12 500cm^?1 spectral region. Among 25 absorption bands of ¹²C₂D₂ rotationally analysed in this spectral region, 17 are newly observed. They include one II_u-Σ⁺ _g and thirteen Σ⁺ _u-Σ⁺ _g bands starting from the vibrational ground state and eleven hot bands from the V ₄ = 1 and V ₅ = 1 lower states. The rotational structure of two excited levels is affected by a strongly J-dependent interaction with a perturber which induces intensity transfer to extra lines. The coupling is identified as a I-resonance interaction with δ_u dark states and the vibrational assignment of the perturbers is discussed. Two Σ-Σ bands of the ¹²C¹³ CD₂ species, present in natural abundance in the sample, could also be identified and rotationally analysed. Most of the corresponding excited vibrational levels of ¹²C₂D₂ were unambiguously assigned using the polyad model [Herman, M., el idrissi, M. I., Pisarchik, A., Campargue, A., Gaillot, A.-C., Biennier, L., di lonardo, G. and Fusina, L., 1998, J. chem. Phys., 108, 1377] which allows vibrational energies and B _V rotational constants to be predicted. In particular the previously highlighted 1/244 anharmonic resonance is confirmed by energy and intensity features in several {(V ₁, V ₂, V ₃, V ₄ = 0, V ₅ = 0),(V ₁ ?1, V ₂ + 1, V ₃ V ₄ = 2, V ₅ = 0)} dyads. Significant deviations between predicted and experimental energy levels are observed for a few levels and discussed.     

The infrared spectrum of gaseous cis-d2-ethylene below 1400 cm−1

Three infrared active fundamental bands of cis-d₂-ethylene have been studied at a resolution of ca. 0.030 cm⁻¹: the type-c band ν₇ and the two type-a bands ν₆ and ν₁₂. From a simultaneous analysis of infrared ground state combination differences due to ν₇ together with microwave measurements, a set of ground state rotational and centrifugal distortion constants has been obtained. For all three bands upper state spectroscopic constants are determined, and perturbations are identified. The K′_a = 4 level in ν₇ is perturbed locally by a higher order c-Coriolis resonance with ν₈. ν₆ is globally perturbed by first-order a-Coriolis resonances with ν₄ and ν₈. For ν₁₂ a higher order c-type Coriolis resonance with 2ν₁₀ is of importance for several K_a levels, and the constants for ν₁₂ have been obtained taking this interaction into account. In addition, a Coriolis resonance parameter and some constants for 2ν₁₀ have been determined.     

Laser infrared spectroscopy of vinyl fluoride in the 1280–1400 cm−1 region

The infrared spectra of CH₂=CHF have been investigated in the ν₅ and ν₆ band regions between 1280 and 1400?cm^?1, at a resolution of about 0.002?cm^?1, using a tunable diode laser spectrometer. These vibrations of symmetry species A′ give rise to a/b-hybrid bands with different contributions from both the components. Spectral analysis resulted in the identification of 1565 (J≤46, K _a ≤11) and 1651 (J≤48, K _a ≤15) transitions of the ν₅ and ν₆ fundamentals, respectively. Both bands are perturbed by the nearby states ν₈?+?ν₉ and ν₉?+?ν₁₁ through different Coriolis resonances and an anharmonic interaction. Using Watson's A-reduction Hamiltonian in the I^r representation and perturbation operators almost all the transitions have been fitted simultaneously to a model including six resonances within the tetrad ν₅/ν₆/ν₈?+?ν₉/ν₉?+?ν₁₁. A set of spectroscopic constants for the ν₅ and ν₆ bands, as well as parameters for the dark states ν₈?+?ν₉ and ν₉?+?ν₁₁ and coupling constants, have been determined. From spectral simulations the dipole moment ratio |Δμ _a /Δμ _b | was estimated to be 0.6?±?0.1 and 2.0±0.3 for the ν₅ and ν₆ bands, respectively.     

Laser spectroscopy of perturbed states of BaO in the region above 32 000 cm−1

The excitation spectrum of BaO in the region above 32 000 cm⁻¹ was investigated with a frequency-doubled pulsed dye laser. We have observed fully developed rotational structures of the C¹Σ⁺-X¹Σ⁺ transition. The analysis of the vibrational states v′ = 0 through 7 leads to a large number of perturbations. This spectroscopic information in combination with the observation and rotational analysis of transitions to several new electronic states allows a systematic summary, which gives more than eight electronic states in the investigated region. Besides the known states B, C, D and c, we find four new bound states, designated by E, F, G, and H. For all states molecular constants are given. The discussion of possible molecular electron configurations leads to classifications of the molecular electronic states. Our results on the vibrational levels v′ = 0 to 3 are in reasonable agreement to the optical-optical double resonance work of R. A. Gottscho, P. S. Weiss, and R. W. Field [J. Mol. Spectrosc. 82, 283–309 (1980)], but show several new details.     

The high-resolution infrared spectrum of HBF2: The 201 band near 1164 cm−1

The type-B totally symmetric stretching fundamental ν₂ (near 1164 cm⁻¹) of difluoroborane has been recorded. Rotational and centrifugal distortion constants have been evaluated for the two isotopic species H¹⁰BF₂ and H¹¹BF₂, in both the ground and 2¹ levels. The spectrum has been found to be regular, with no perturbations and no new information on the position of the missing fundamental ν₆.     

High resolution FTIR spectra of AsD3 in the 20-1000 cm−1 region. The ground, 98, v2 = 1 and v4 = 1 states

The pure rotational spectrum of the near-spherical oblate symmetric top AsD₃ has been recorded in the 20–120cm^?′ region with a resolution of 2.3 × 10^?3 m^?1 employing an FT interferometer. Rotational transitions with 5 ? J ? 29 and 0 ? X ? 25 of the ground state (GS) and the v₂ = 1 and v₄ = 1 excited states have been assigned. Splittings were observed for the GS, 98, K = 3 and 6 levels, the K = 3 levels of v₂ and the kl = ?2, 1, 4 and 7 levels of v₄. Furthermore the x,y Coriolis coupled v₂ and v₄ bands, v ⁰ ₂ = 654.4149cm^?1, and v ⁰ ₄ = 714.3399 cm^?1, have been examined with a resolution of 2.4 × 10^?3 cm^?1, and ca. 2500 allowed and 336 ‘forbidden’ lines with J′_max = 31 and K′_max = 28 have been assigned. Appropriately weighted GS data comprising FIR lines, allowed and ‘forbidden’ (up to ΔK = ±6) GS combination differences, mmw data, and ΔJ = 0, ΔK = ±1 distortion moment transitions were fitted together, and GS parameters complete through H parameters have been determined. Two different reductions of the Hamiltonian, either with ΔK = ±6 (h₃) or ΔK = ±3 (ε) off-diagonal elements, have been employed. Equivalence of these reductions up to J = 22 was established while for J > 22 the ε reduction is superior. The v₂ and v₄ data have been fitted with two equivalent models based on different reductions of the rovibrational Hamiltonian. In addition to the dominating x,y Coriolis resonance, ζ ^y ₂₄ 0.520, Δ(k ? l) = ±3 and ±6 interactions are important and were accounted for by the models. The transition moment ratio |M₄: M₂| =0.75 has been determined, with a positive sign of the product M ₂ζ ^y ₂₄ M ₄. An improved r₀ structure, r₀(AsD) = 1.51753 Å and α₀(DAsD) = 92.000°, has been determined.     

The pentad of 12CD4: Line parameter analysis of the IR spectrum in the range 1775–2350 cm−1

In a previous paper (J.-E. Lolck, G. Poussigue, E. Pascaud, and G. Guelachvili, J. Mol. Spectrosc. 111, 235–274 (1985)), we presented the first comprehensive assignment and wavenumber analysis of high-resolution (nearly Doppler limited) rotation-vibrational spectra of the interacting upper states of the ν₁, ν₃, 2ν₂, ν₂ + ν₄, and 2ν₄ bands of the ¹²CD₄ pentad. The present paper continues this work by describing the determination and quality estimation of experimental infrared line strengths from the Fourier transform spectra. These line strengths are interpreted in terms of a theoretical model which contains, as parameters, the dipole moment derivatives and the main Hermann-Wallis coefficients of the infrared-allowed bands: ν₃(F₂), ν₂ + ν₄(F₂), and 2ν₄(F₂). This model also explains the appearance of infrared transitions to upper states, forbidden in infrared in an isolated state approach, through the mixing of states caused by the intervibrational interactions. The intensity analysis leads to the determination of all six parameters in the model and to a reproduction of the experimental intensities with a precision comparable to the experimental accuracy of 10 to 15%.     

The FT absorption spectrum of 13CH12CH: rotational analysis of the vibrational states from 3800 to 6750 cm−1

Thirty four cold bands and 37 hot bands are reported from the high resolution FT absorption spectrum of ¹³CH¹²CH, all leading to vibrational states located between 3800 and 6750?cm^?1. Each band has been vibrationally assigned and rotationally analysed. The band centres and rotational constants are listed.     

A comprehensive model to predict the microwave spectrum of propyne in the region 17–70 GHz for the ground and v10 = 1, 2, 3, 4, 5 vibrational states

A comprehensive model for predicting rotational frequency components in various v₁₀ vibrational levels of propyne was developed. A number of components of the rotational spectra in the ground and v₁₀ = 1, 2, 3, 4 excited vibrational states of propyne in the frequency range 17–70 GHz have been obtained. Molecular constants for these vibrationally excited states have been determined from more than 100 observed rotational transitions. From these experimentally observed components and a model based upon first principals for C_3v molecules, rotational constants have been expressed in a form which enables one to predict rotational components for vibrational levels for propyne up to v₁₀ = 5. The model also appears to be useful in predicting rotational components in more highly excited vibrational levels but data were not available for comparison with the theory. Experimentally measured frequencies are presented and compared with those calculated using the results of basic perturbation theory.