High-resolution vibration-rotation spectra of monochloroacetylene (HCCCl) have been recorded in two different wavenumber regions. Fourier transform infrared interferometer measurements in the 4000-10000 cm(1) range have been performed with a resolution of 0.005-0.016 cm(1) and titanium: sapphire ring laser intracavity photoacoustic measurements in the 12 500-12 600 cm(1) and 12 800-12 860 cm(1) regions have been carried out with a Doppler-limited resolution of about 0.02 cm(1). Altogether, 40 vibrational bands belonging to the HCC35 Cl and 15 bands belonging to the HCC37 Cl isotopic species have been rotationally assigned. A vibrational model, based on the conventional rectilinear normal coordinate theory including anharmonic Fermi, Darling-Dennison and vibrational l-type doubling resonances, has been used to attach vibrational labels to the bands. This approach is found to describe well the rovibrational energy level structure at least in the energy range covered in this work. The model shows that the CH oscillator becomes decoupled from the rest of the molecule as vibrational energy increases.

High-resolution vibration–rotation spectra of gas-phase deuterobromoacetylene have been recorded in the 240–990 cm−1infrared region. The analyzed band systems are rich in hot bands and have a high density of lines. Five band systems and a total of 124 vibration–rotation bands of the isotopic species DCC79Br and DCC81Br have been rotationally analyzed. Accurate rotational parameters and vibrational wavenumbers for 33 vibrational states of each species have been obtained from the rotational analysis.ldoubling and rotationallresonance have been observed on some states and the respective resonance parameters have been obtained through nonlinear least-squares optimization. A Fermi resonance block model with perturbation terms has been used for the analysis of the vibrational states. With optimized parameters, the model produces root-mean-square deviations of observed − calculated wavenumbers of about 0.3 cm−1for both isotopic species.

Photoacoustic overtone spectra of monobromoacetylene, HCCBr, have been recorded in the wavenumber region 11600–13400 cm−1using a titanium:sapphire ring laser spectrometer. All together, eight overtone bands of HCC79Br and eight bands of HCC81Br have been observed in the rotational analysis. A Fermi resonance model based on conventional normal coordinate theory has been used to vibrationally assign the rotationally analyzed bands. The resonance model employed reproduces well the observed vibrational band origins and rotational constants.

The FTIR spectrum of H3SiD in the 4100-4500-cm-1 region was recorded at Doppler-limited resolution, and four bands were studied. At lower wavenumbers, two strong bands, which in the local mode picture can be assigned to (200, E) (nu0 = 4308.5667 cm-1) and (200, A1) (nu0 = 4307.8441 cm-1), were analyzed, and at higher wavenumbers, two weaker bands, namely (110, E) at 4378.1950 cm-1 and (110, A1) at 4375.9763 cm-1, were analyzed. A total number of approximately 1900 lines in the strong dyad and 1000 lines in the weak one were assigned and fitted with standard deviations of the residuals approximately 0.0008 cm-1. The strong system (200) is close to local mode behavior, with no x, y Coriolis term needed and only a small z Coriolis term, and simple arithmetic relations between vibration-rotation parameters are fulfilled as expected. The local mode behavior of the weak system (110) is less pronounced, but z and x, y Coriolis effects are smaller than in the Si-H stretching fundamentals. Comparison of computed and observed spectra provided a good estimate for the ratios of transition moments of the different bands: they are, in absolute value, proportional to 3.5:1.75:1:1 for (200, E), (200, A1), (110, E), and (110, A1), respectively. Copyright 1998 Academic Press.

Spectra of a natural sample of hydrogen telluride as well as a spectrum of monoisotopic H-2 Te-130 have been recorded by means of Fourier transform spectrometry with a resolution of 0.003 cm(-1) in the spectral domain 7.5-4.3 mu m where it is easy to observe the main absorbing bands nu(1) and nu(3). We have located and assigned for the first time the 2 nu(2) band which appears in the lower wavenumber range of the recorded spectral domain near 1700 cm(-1). It proved necessary to treat simultaneously the three states (020), (100), and (001), nu(1) and nu(3) are indeed Coriolis-coupled vibration-rotation bands and it was observed that a few rotational levels of (001) could not be fitted to within their experimental accuracy without considering the second-order Coriolis interaction between the rotational levels of (020) and (001). In this way all the experimental levels were calculated to within the experimental uncertainty, and precise sets of vibrational energies and rotational and coupling constants were obtained for the seven most abundant H2Te isotopic species, namely H-2 Te-130, H-2 Te-128, H-2 Te-126, H-2 Te-125, H-2 Te-124, H-2 Te-123, and H-2 Te-122. For the most abundant isotopic species H-2 Te-130 the bands centers arenu(0)(2 nu(2)) = 1715.9568, nu(0)(v(1)) = 2065.2709, nu(0)(nu(3)) = 2072.1101 cm(-1). (C) 1997 Academic Press.

High resolution Fourier transform spectra of a natural and a Te-130 monoisotopic sample of H2Te have been recorded at a resolution of 0.0022 cm(-1) in the 11.6 mu m spectral region, as well as a spectrum of a natural sample of H2Te at a resolution of 0.0051 cm(-1) in the 2.4 mu m region. In the 11.6 mu m region the main absorbing band is the nu(2) band, the analysis of which was rather easy. On the other hand, in the 2.4 mu m region three bands are absorbing, namely 2 nu(1), nu(1) + nu(3), and 2 nu(3), the last being much weaker than the others. The analysis in this spectral domain was much more difficult because of resonances, Indeed it proved not possible to reproduce the observed lines without taking into account the Darling-Dennison interaction between the levels of the (200) and (002) states and the Coriolis interactions between the levels of(200) and (101) and between those of (101) and (002). Considering these interactions allowed us to calculate very satisfactorily all the experimental levels, and precise sets of vibrational energies and rotational and coupling constants were obtained for the seven most abundant H2Te Isotopic species, namely (H2Te)-Te-130, (H2Te)-Te-128, (H2Te)-Te-126, (H2Te)-Te-125, (H2Te)-Te-124, (H2Te)-Te-123 and (H2Te)-Te-123. For the most abundant species, (H2Te)-Te-130, the band centers in cm(-1) are nu(0)(nu(2)) = 860.6563, nu(0)(2 nu(1)) = 4062.8542, nu(0)(nu(1) + nu(3)) = 4063.3697, and nu(0)(2 nu(3)) = 4137.0454, These results, combined with those obtained for other vibrational states, have been used to derive the equilibrium rotational constants and their corrections. Finally, by neglecting the electronic corrections, the equilibrium structure of (H2Te)-Te-130 was obtained as follows: r(e) (Te-H) = 1.65 145(10) Angstrom, alpha(e) (HTeH)= 90.2635(90)degrees. (C) 1997 Academic Press.

Infrared spectra oftrans-monodeutero-diimide, HNND, have been recorded between 760 and 3250 cm−1at a resolution of ca. 0.005–0.007 cm−1, from which the fundamental bands ν1, ν4, ν5, and ν6of this isotope have been studied. A detailed analysis of thea,b-Coriolis interacting band system ν5, ν6near 1100 cm−1is presented. The ν4band at 1475 cm−1has been analyzed by a model includingc-Coriolis and ΔKa= ±2 vibrational resonance with the close lying ν3band at 1538 cm−1. Only 18 transitions in ν3which obtain their intensity through interaction with the ν4band have been assigned. Together with the observed perturbation effects in ν4they provide valuable information for the ν3level, too. In the ν1band around 3110 cm−1numerous local crossings due to vibrational andc-Coriolis interactions with the unobserved binary combinations 2ν3, ν3+ ν4, and 2ν4have been identified. The present analyses yield a number of spectroscopic constants for the ν1, ν3, ν4, ν5, and ν6levels and various interaction constants. From a simultaneous ground state combination difference analysis of the four observed bands the following ground state rotational constants are obtained:A0= 7.384213(4) cm−1,B0= 1.1959457(6) cm−1, andC0= 1.0255827(6) cm−1.

High-resolution Fourier transform spectra of a natural sample of hydrogen telluride and of monoisotopic (H2Te)-Te-130 have been recorded in the 3.2-4-0 mu m spectral region where the 3 nu(2), nu(1) + nu(2) and nu(3) bands of this molecule absorb. The (030) rotational levels were least-squares fitted using a Watson-type Hamiltonian whereas it proved necessary to consider the strong Coriolis interaction coupling the (110) and the (011) rotational levels. In this way all the experimental levels were calculated to within their experimental uncertainty and precise sets of vibrational energies and rotational and coupling constants were obtained for the (030), (110), and (011) vibrational states of (H2Te)-Te-130, (H2Te)-Te-128, (H2Te)-Te-126, (H2Te)-Te-125, (H2Te)-Te-124, (H2Te)-Te-123, and (H2Te)-Te-122. The band centers for the most abundant isotopic species, namely (H2Te)-Te-130, are:nu(0)(3 nu(2)) = 2565.4428, nu(0)(nu(1) + nu(2)) = 2911.4098, nu(0)(nu(2) + nu(3)) = 2915.9599 cm(-1).(C) 1997 Academic Press.

The gas-phase IR spectra of thea,b-Coriolis interacting band system ν4,ν6around 950 cm−1and the ν5band around 2300 cm−1of N2D2have been recorded with a resolution of ca. 0.005 and 0.007 cm−1, respectively. In the ν5and ν6bands botha- andb-type components are observed. In ν4thec- and a parallel-type component which obtains its intensity from the stronga-Coriolis resonance with ν6are observed. In addition, ΔKa= ±2 band components which are due to strongb-Coriolis perturbation are observed in both ν4and ν6. From a simultaneous ground state combination difference analysis of all three bands the following ground state constants are obtained:A0= 6.0245856(22) cm−1,B0= 1.08957754(33) cm−1, andC0= 0.91955624(33) cm−1. The upper state energies from the ν4, ν6band system have been analyzed using a dyad model including first and higher ordera- andb-Coriolis interactions between these levels. In the analysis of the ν5band weak higher orderc-type and vibrational type ΔKa= ±2 interactions with the unobserved combination band ν3+ ν6are taken into account. Upper state spectroscopic constants for all three levels and a number of interaction constants have been determined from these analyses.

The third stretching overtone region of a natural sample of stibine, SbH3, has been studied with high resolution infrared spectroscopy and the fifth and the sixth overtone region with Ti:Sapphire ring laser intracavity photoacoustic spectroscopy. The third overtone consists of a local mode pair of bands (400A1/E) which have been rotationally assigned both for 121SbH3 and 123SbH3 with a vibration-rotation model based on rectilinear normal coordinates. The vibrational dependencies of the model parameters are explained well with a simple block diagonal vibrational model. An extension of the standard vibration-rotation model is used to show that the upper state rotational energy level structures of both isotopic species are close to the rotational structure of an asymmetric rotor. High resolution laser spectrum of the fifth overtone consisting of a local mode pair of bands (600A1/E) shows severe perturbations in the upper state rotational structure. The (510A1/E) and (700A1/E) bands have been recorded with low resolution. All experimentally known vibration-rotation band origins of 121SbH3 have been reproduced well with a curvilinear internal valence coordinate system based Fermi resonance local mode model. The potential energy surface obtained agrees well with recent ab initio results.

In the present work, we study the spectrum of the H2Te molecule in the submillimeter-wave and far infrared region. An important aim of this investigation is the further experimental characterization of the anomalous "four-fold cluster effect" exhibited by the rotational energy levels in the vibrational ground state of H2Te. The spectrum in the region 90-472 GHz was measured with a source-modulated millimeter-wave spectrometer and that between 600 and 1600 GHz with a far-infrared sideband spectrometer. The far infrared spectrum from 30 to 360 cm-1 was measured with a Bruker IFS 120 HR interferometer attached to a 3 m long cell. We have assigned 224 submillimeter-wave lines and 1695 FIR lines. These observed data were supplemented by a large number of ground state combination differences derived from rotation-vibration bands of H2Te, and the resulting large data set was analyzed by means of a modified Watson Hamiltonian. Accurate sets of rotational and centrifugal distortion constants for all eight tellurium isotopomers were obtained.

Infrared spectra of [2-13C]allene (H2C[formula]13C[formula]CH2) between 1300 and 3300 cm−1covering the ν7, ν9+ ν11, 2 ν10, ν6, ν5, and ν8bands have been studied at a resolution of ca. 0.004 cm−1. Spectroscopic constants are derived from single subband analysis of these bands and various perturbations are discussed. A detailed analysis of the[formula]band system is performed from a model taking into account Fermi resonance between ν7and[formula]higher order anharmonic resonance between ν7and[formula]higher order anharmonic resonance between[formula]and rotationall-type resonances within ν9+ ν11. The 2ν10band has been analyzed using a model taking into account rotationall-type resonances within 2ν10and (x,y)-Coriolis interactions with ν4+ ν10and ν7+ ν11. Both analyses yield a number of spectroscopic constants for the levels included in the models as well as various interaction constants.

The lowest fundamental level ν11 in 2-13C-allene, H2C[]13C[]CH2, has been studied from a high resolution infrared spectrum of the ν11 band together with lower state combination differences obtained from high resolution infrared measurements of the hot bands ν7 + ν11 − ν11, ν9 + ν11 − ν11, ν10 + ν11 − ν11, and 2ν10 + ν11 − ν11. From a simultaneous analysis of 4592 energy levels and combination differences for the ν11 level a set of spectroscopic constants has been obtained with a model taking into account the two types of rotational l-type resonance allowed for this molecule. Subband constants for the various hot bands ν7 + ν11 − ν11, ν9 + ν11 − ν11, ν10 + ν11 − ν11, and 2ν10 + ν11 − ν11 assigned in this study are summarized in tables.

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The infrared spectra of the ν8 band of natural methylene chloride and isotopically pure CH235Cl2 have been recorded at a resolution of 0.0025 cm−1 in the range 1100-1400 cm−1 with a Bruker IFS 120 HR Fourier transform interferometer. The spectrum of the ν8 fundamental band has been analyzed for the most abundant isotopic species CH235Cl2 and CH235Cl37Cl, as well as the ν4 + ν8 − ν4 hot band of CH235Cl2. From a rotational analysis, excited state constants up to quartic terms have been obtained, using Watson′s A-reduction Hamiltonian in the Ir representation. No perturbations have been observed. The standard deviations of the fits vary from 0.44 × 10−3 to 0.62 × 10−3 cm−1.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The fifth and the seventh stretching vibrational overtone bands of a monoisotopic stannane sample, 116SnH4, have been recorded with Doppler limited resolution using intracavity photoacoustic technique with a titanium:sapphire ring laser. Both band systems resemble closely symmetric top parallel bands in agreement with local mode predictions. The rotational fine structures of these bands have been analyzed with the symmetric top energy level formula and with a spherical top Hamiltonian which treats the problems as interacting rotational levels of A1 and F2 vibrations. Altogether about 200 vibration–rotation transitions have been assigned for both band systems. The fifth overtone band system shows some minor local perturbations due to interactions with bending states. The seventh overtone band is completely unperturbed. The observed vibration–rotation parameters are in good agreement with the ones calculated from a simple vibrational model.

The spectrum of chlorodifluoromethane (CFC-22) has been investigated in the infrared region. Spectra of CHF2Cl were recorded at room temperature with high resolution (0.0017 cm−1, Bruker IFS 120 HR) in the region between 335 and 450 cm−1. The spectral analysis of CHF235Cl (isotopically pure sample) allowed us to assign more than 5500 lines (J ≤ 76) to the ν9b-type band (ν0 = 366.1972 cm−1) and more than 6100 lines (J ≤ 74) to the ν6a/c-hybrid band (ν0 = 412.9286 cm−1). These two bands interact through both c-type and a-type Coriolis couplings. The addition of microwave and millimeter-wave data (see accompanying paper by Z. Kisiel, L. Pszczółkowski, G. Cazzoli, and G. Cotti, J. Mol. Spectrosc.173, 477-487, 1995) to these IR transitions allowed a global fit to be performed. The resulting molecular parameters are much better defined than when each type of transition is fitted separately. It was also found, by simulating the spectrum, that the dipole moment ratio between the a and c components of ν6 is about 1.5 and the corresponding ratio of ν9 and ν6a is about 2. Moreover, results will be given concerning CHF237Cl, obtained from a natural abundance sample as well as approximate bandcenters for several hot bands, which were not analyzed in detail.

The infrared spectrum of a sample of natural monobromoacetylene (HCCBr) has been recorded with the Bruker IFS 120 Fourier spectrometer in the wavenumber region 1100-9800 cm−1 with a resolution close to the Doppler limit. The 2ν4, ν1, 2ν1, and 3ν1 band systems have been analyzed. Altogether, 24 vibrational bands belonging to the HCC79Br and 26 bands belonging to the HCC81Br isotopic species have been observed and rotationally assigned. An anharmonic resonance model based on rectilinear normal coordinate theory has been used to produce the vibrational assignments for the observed bands.