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  • 1
    Digitale Medien
    Digitale Medien
    Spectra of the rare gas hydrides. IV. Three new bands of argon deuteride involving a low-lying "p'' Rydberg state (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7093-7110 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Three fairly strong emission bands of ArD at 6100, 6900, and 10 200 cm−1 have been studied at high resolution. They show very different structures: the first exhibits only Q-form branches, the second P, R, O, and S-form branches, and the third Q, S, and O-form branches. The rotational analysis of each of these bands is not trivial, mainly because the upper state of the first which proved to be also the lower state of the second and third is strongly affected by l uncoupling [i.e., transition to Hund's case (d)] and as a result the usual method of combination differences cannot be applied in their analysis. However, more sophisticated combination differences have been found between the three bands which lead to unambiguous assignments of rotational quantum numbers and thus to rotational constants. It was found that the upper state of the 6100 cm−1 band can be most conveniently represented as a p(2Σ,2Π) complex. This assumption, together with the theoretical selection rules for such a case, led to a full understanding of the structure of the three bands.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463535
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  • 2
    Digitale Medien
    Digitale Medien
    The far infrared spectrum of C3O2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2299-2316 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The far infrared spectrum of carbon suboxide, 12C316O2, has been recorded at a resolution of 0.003 cm−1 in the region from 15 to 130 cm−1 with a Bomem interferometer. Altogether 18 bands involving the excitation of up to 8 quanta in the low frequency quasilinear bending mode ν7 were analyzed rotationally. A total of 1320 far infrared lines together with 231 microwave lines taken from Karyakin et al. [J. Mol. Spectrosc. 94, 283 (1982)] have been fitted to an effective model. Improved effective constants have been obtained for all the l sublevels of v7=0 to 4 and for l=1 of v7=5. Constants have been obtained for the first time for the levels 53 and 55 and some of the l sublevels of v7=6, 7, and 8. Data for the lower lying levels were fitted to a realistic linear model and some data were also fitted to a bent model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460938
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  • 3
    Digitale Medien
    Digitale Medien
    Frequency and intensity analysis of the ν3, ν4, and ν6 bands of formaldehyde (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 646-654 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The infrared spectra of the ν3, ν4, and ν6 bands of formaldehyde in the region from 890 cm−1 to 1580 cm−1 have been obtained at high resolution using tunable diode laser (TDL) and Fourier transform-infrared (FT-IR) spectroscopy. The transition frequencies have been analyzed using a Hamiltonian including terms through sextic in centrifugal distortion and including five interstate vibration–rotation coupling terms. Excited state pure rotational transitions are also included in the data, and their frequencies are reproduced well. Individual measured line intensities are used to determine dipole derivatives and band strengths using the fully coupled, asymmetric top eigenvectors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457170
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  • 4
    Digitale Medien
    Digitale Medien
    The bending vibrational levels in C2D2 (X˜ 1Σ+g) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3407-3414 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Improved sets of data have been recorded and analyzed in order to study the bending rovibrational energy levels of C2D2, in the regions of the ν5–ν4 difference band (FIR) and of the ν5 fundamental band (IR). A matrix model is setup to deal with a Darling–Dennison coupling between sets of bending levels as well as with the usual l-type resonances. A simultaneous fit of the new data together with earlier microwave measurements produces an extended set of very accurate parameters, including for the first time in C2D2 s45 and qkt.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459763
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  • 5
    Digitale Medien
    Digitale Medien
    The torsional spectrum of CD3CD3 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2387-2394 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The far-infrared spectrum of gaseous CD3CD3 has been measured in the region of the torsional fundamental under relatively large pressure-path length conditions. The observations were made using a modified Bomem spectrometer at a resolution of 0.016 cm−1, an absorption path of 20 m, and a gas temperature and pressure of 168 K and 80 Torr, respectively. The prominent features of the spectrum are the P, Q, and R branches of the torsional fundamental (v4=1←0) and the Q branch of the first torsional overtone (v4=2←1). The P and R branches of the fundamental consist of peaks about 0.2 cm−1 wide due to unresolved structure. In addition, a very high resolution (0.0014 cm−1) spectrum of the lowest lying degenerate fundamental ν9 of CD3CD3 was obtained. From the combined intensity and frequency analyses of the far-infrared spectrum and 442 lower state combination differences in ν9 and its associated hot band ν9+ν4−ν4, the effective leading coefficients V˜3=989.10(68) cm−1 and V˜6=9.47(29) cm−1 in the Fourier expansion of the hindering potential were determined. The rotational constant B was found to be 13 802.658(39) MHz and four distortion parameters were obtained. The torsional dipole constants μ⊥ and μ(parallel)−μ⊥ were determined to be 7.41(74) and −19.9(2.0) μD, respectively. The experimental values of μ⊥ and μ(parallel)−μ⊥ are shown to be in good agreement with values calculated from theoretical expressions. The shape of the torsional bands can be reproduced in detail with the model adopted here.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459862
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  • 6
    Digitale Medien
    Digitale Medien
    The far infrared spectrum of H2O2. First observation of the staggering of the levels and determination of the cis barrier (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1504-1510 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: High resolution spectra of H2O2, recorded by means of Fourier transform spectroscopy between 30 and 460 cm−1, have been analyzed leading to the determination of the rotational levels of the torsional states (n,τ) for n=0,1,2,3. In order to reproduce these energy levels, Watson type Hamiltonians have been used and it has been possible to observe a staggering of the levels with n=2 and 3 caused by the cis barrier. The torsional band centers have then been fitted using a torsional Hamiltonian of the form {Bγγ,J2γ} +V(γ) with the potential function V(γ) written as V(γ)=V1 cos 2γ+V2 cos 4γ+V3 cos 6γ+V4 cos 8γ where the torsional coordinate 2γ is the dihedral angle defining the relative position of the two O–H bonds. The potential constants in cm−1 are V1=1036.97±23.1 cm−1, V2=657.53±5.2 cm−1, V3=50.89±3.3 cm−1, V4=2.524±0.83 cm−1 which correspond to barrier heights Vtrans =387.07±0.20 cm−1, Vcis =2562.8±60 cm−1, and to a potential minimum located at 2γ=111.9°±0.4° from the cis configuration. It is also shown that the rotational constants derived from the fit to the experimental rotational levels cannot be reproduced using a model which does not take into account vibrational corrections.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457110
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  • 7
    Digitale Medien
    Digitale Medien
    Overtone and hot-band assignments in the 2{ν3, ν6} levels of CHD3 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 5508-5518 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Assignments have been carried out for the 2ν3/(ν3+ν6)/2ν6 (triad)←ground state overtone bands and the triad←ν3/ν6 hot-band system of CHD3. A vibrational extrapolation method, using correspondences between a spherical-tensor formalism and the more conventional description of symmetric-rotor spectra, was used to facilitate the assignment and analysis of these bands. The resulting assignments have been confirmed by time-resolved double-resonance measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467169
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  • 8
    Digitale Medien
    Digitale Medien
    Fourier transform spectroscopy of the CO-stretching band of C-13 methanol in the torsional ground state (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6444-6455 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The Fourier transform spectrum of the CO-stretching fundamental band of 13CH3OH has been investigated at 0.002 cm−1 resolution. For the n=0 torsional ground state, 35 subbands containing some 2300 lines have been identified for K values from 0 to 10 for the three torsional symmetries A, E1, and E2 up to J values typically well over 30. The assigned transitions have been fitted to J(J+1) power-series expansions to obtain subband origins and sets of phenomenological state-specific parameters describing the J dependence of the subbands. These parameters reproduce the observed wave numbers to within the experimental uncertainty of ±0.0005 cm−1 for unblended lines, except when particularly large asymmetry shifts or perturbations due to Fermi or Coriolis resonances are present. The subband origins have been fitted to effective molecular constants for the excited CO-stretching state and a torsional barrier of 378.7(8) cm−1 is found, representing a 1.3% increase over the ground state value. A wide variety of global or J-localized perturbations has been seen, and most of the interacting states have been identified. New assignments have been obtained for far-infrared laser lines optically pumped by the 10R(2) and 9P(12) CO2 laser lines. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.469359
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  • 9
    Digitale Medien
    Digitale Medien
    Fourier transform spectroscopy of torsionally excited C-13 methanol in the CO-stretching band (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3406-3418 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Torsionally excited n=1 and n=2 subbands of the CO-stretching fundamental have been assigned in the Fourier transform infrared spectrum of 13CH3OH recorded at a resolution of 0.002 cm−1. For the n=1 torsional state, subbands with K values up to 7 have been identified for A torsional symmetry and up to 5 for E symmetry. For n=2, four subbands have so far been assigned. Subband origins have been obtained by fitting the observed wave numbers to J(J+1) power-series expansions. The expansion parameters represent the data compactly to close to the experimental uncertainty in the absence of line blending or perturbations. Significant downshifting of the n=1 origins is observed, correlated closely with proximity to the n=0 OH-bending state. J-localized perturbations have been observed and characterized for several subbands. Two of the far-infrared laser lines optically pumped by the 10R(14) CO2 laser line have been assigned. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.472226
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  • 10
    Digitale Medien
    Digitale Medien
    Intensity analysis of the torsional spectrum of CH3CH3 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3981-3988 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The far-infrared spectrum of gaseous CH3CH3 has been measured in the region of the torsional fundamental under relatively large pressure-path length conditions. Observations were made at resolutions of 0.08, 0.02, and 0.016 cm−1 and under various experimental conditions using two different Fourier transform spectrometers. In addition, a very high resolution (0.0014 cm−1) spectrum of the lowest lying degenerate fundamental ν9 was obtained. From a frequency analysis of the far-infrared spectrum and 737 lower state combination differences in ν9 and its associated hot band ν9+ν4−ν4, an improved set of torsion–rotation parameters was obtained. An intensity analysis of the torsional bands was carried out to obtain torsional dipole moments. The torsional dipole components μ⊥ and (μ(parallel)−μ⊥ ) were determined to be 9.37(70) and −31.7(2.0) μD, respectively. These experimental values are in good agreement with calculated values of μ⊥=10.13 μD and (μ(parallel)−μ⊥ )=−35.10 μD. The shape of the torsional bands can be reproduced in detail with the model adopted here.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.462937
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