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  • 1985-1989  (4)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    The structure of the CO2–CO2–H2O van der Waals complex determined by microwave spectroscopy (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5964-5970 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational spectra of CO2 –CO2 –H2 O, CO2 –CO2 –D2 O, 13 CO2 –13 CO2 –H2 O and CO2 –CO2 –H2 18 O have been measured using a pulsed-molecular-beam Fabry–Perot Fourier-transform microwave spectrometer. An asymmetric top spectrum is observed with rotational constants, A=3313.411(5) MHz, B=1470.548(3) MHz, and C=1308.850(3) MHz for the normal species. The dipole moment obtained is μT =μb =1.989(2) D. Only b-type transitions are observed with the transitions showing a 3 to 1 intensity alternation depending on whether Ka +Kc is odd or even, respectively. This indicates a structure with twofold symmetry with the C2v axis of the water subunit aligned with the C2 axis of the complex. The CO2 subunits lie in a plane which is perpendicular to the C2 axis and located 2.47 A(ring) below the oxygen atom of the water subunit; the C–C bond length is 3.413(2) A(ring). The orientation of the CO2 subunits in CO2 –CO2 –H2 O is very similar to that observed in CO2 –CO2 although the C–C bond length is 0.19 A(ring) shorter in the trimer. The C–O bond distances between the H2 O and two CO2 subunits are both 3.00(2) A(ring) which is 0.16 A(ring) longer than that found in the CO2 –H2 O dimer. The hydrogens of the H2 O subunit are directed away from the CO2 –CO2 plane although their angular orientation around the b axis is not well determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456362
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Water–hydrocarbon interactions: Structure and internal rotation of the water–ethylene complex (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 725-732 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational spectra of C2H4–H2O and C2H4–D2O were measured using the molecular beam electric resonance technique. The rotational and centrifugal distortion constants obtained for C2H4–H2O are: B+C=7274.747 (24), B−C=371.103 (8), A=25 858.4 (36), ΔJ=0.0279 (17), ΔJK=1.7352 (66), and δJ=0.002 99 (22) MHz. The dipole moment for both isotopic species is 1.094 (1) D. The structure derived from an analysis of the rotational constants and dipole moment is nonplanar with Cs symmetry. The water molecule is singly hydrogen bonded perpendicular to the plane of the ethylene; i.e., into the π system. The plane of the water bisects the C–C bond. The hydrogen bond length is 2.48 A(ring). Splittings are observed in the rotational transitions of C2H4–H2O but not in C2H4–D2O. These are assigned to excited torsional levels of the hindered internal rotation of the water with respect to the ethylene. The barrier height is estimated to be V2=1.0±0.2 kcal/mol which is surprisingly high for this weakly bound complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451279
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The microwave spectrum of the K=0 states of Ar–NH3 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5512-5518 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of Ar–NH3 has been obtained using molecular beam electric resonance spectroscopy and pulsed nozzle Fourier transform microwave spectroscopy. The spectrum is complicated by nonrigidity and most of the transitions are not yet assigned. A ΔJ=1, K=0 progression is assigned, however, and from it the following spectroscopic constants are obtained for Ar–14NH3: (B+C)/2=2876.849(2) MHz, DJ =0.0887(2) MHz, eqQaa =0.350(8) MHz, and μa =0.2803(3) D. For Ar–15NH3 we obtain (B+C)/2 =2768.701(1) MHz and DJ =0.0822(1) MHz. The distance between the Ar atom and the 14NH3 center of mass RCM is calculated in the free internal rotor limit and obtained as 3.8358 A(ring). In the pseudodiatomic approximation, the weak bond stretching force constant is 0.0084 mdyn/A(ring) which corresponds to a weak bond stretching frequency of 35 cm−1. The NH3 orientation in the complex is discussed primarily on the basis of the measured dipole moment projection and the quadrupole coupling constant. It is concluded that the Ar–NH3 intermolecular potential is nearly isotropic and that the NH3 subunit undergoes practically free internal rotation in each of its angular degrees of freedom. Spectroscopic evidence is presented which indicates that the NH3 subunit also inverts within the complex. These conclusions concerning the internal dynamics in the Ar–NH3 complex support the model initially proposed in our previous study of the microwave and infrared spectra of this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451562
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  • 4
    Electronic Resource
    Electronic Resource
    The rotational spectra of NH3–CO and NH3–N2 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 2472-2480 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational spectra of NH3–CO, ND3–CO, ND2H–CO, NDH2–CO, NH3–13CO, and NH3–N2 have been measured by molecular beam electric resonance. The K=0 ground vibrational state transitions for these species were fit to a linear molecule Hamiltonian and the following constants were obtained for NH3–CO; (B+C)/2 (MHz)=3485.757(2), DJ (kHz)=110.2(2), eQqNaa (MHz)=−1.890(7), μa (D)=1.2477(8). These constants were also determined forND3–CO [3078.440(7), 75.7(8), −2.028(15), 1.2845(9)], NHD2–CO [3202.303(4), 86.8(6), −1.972(11), 1.2686(8)], NH2D–CO [3338.235(4), 98.9(6), −1.916(12), 1.2546(8)], NH3–13CO [3451.684(5), 108.7(7), −1.870(15), 1.2452(8)]. For NH3–N2 (B+C)/2=3385.76(21), DJ =117.(10), and μa =1.069(14). For NH3–CO three ||ΔJ||=1, K=0 progressions were seen along with two ||ΔJ||=1, K=1 progressions, suggesting nonrigidity in the complex. The internal rotation of the NH3 subunit about its C3 axis is expected to be essentially free, but this motion, by itself, is not sufficient to explainthe observed spectra, thus, large amplitude dynamics are occurring in at least two degrees of freedom. The quadrupole coupling constants, eQqNaa indicate that in each of the isotopes of NH3–CO the NH3 subunit has its C3 axis relatively rigidly oriented at an angle of approximately 36° with respect to the line connecting the centers of mass of the two subunits. The structure is not hydrogen bonded; the N atom is closest to the CO subunit. The orientation of the CO subunit is not established. The distance between the N atom and the center of mass of the CO unit (RN–CO) is 3.54(3) A(ring). The spectroscopic constants suggest that the weak bond stretching force constant is quite small (0.01 mdyn/A(ring)) but compatible with the long bond length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450366
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