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  • 1
    Electronic Resource
    Electronic Resource
    The rotational and tunneling spectrum of the H2S⋅CO2 van der Waals complex (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6408-6419 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational spectra of H2S⋅CO2 and two deuterated forms have been observed using a pulsed-beam Fourier-transform microwave spectrometer. For each of the three complexes we assign a-type and c-type transitions which are split into a "weak'' and a "strong'' intensity component. The analysis based on that previously used for the (H2O)2 complex and modified for application to H2S⋅CO2, allowed us to assign internal rotation, inversion tunneling states of the H2S and CO2 units in the complex. The following rotational constants were determined for the ground tunneling state of each species: for H2S⋅CO2, A=11 048.0(26) MHz, B=2147.786(4) MHz, and C=1806.468(4) MHz; for HDS⋅CO2, A=10 769(35) MHz, B=2107.26(24) MHz, and C=1775.83(24) MHz; and for D2S⋅CO2, A=10 356.2(28) MHz, B=2065.376(8) MHz, and C=1746.122(8) MHz. The electric dipole moments were determined for the H2S⋅CO2 and D2S⋅CO2 species, resulting in the values μa=0.410(14) D and μc=0.822(10) D for the H2S⋅CO2 species. The structure of the complex has the CO2 and the S atom of H2S in a T-shaped configuration. The H2S plane is nearly orthogonal to the CO2–S plane with an angle of about 92° and the H2S⋅CO2 center-of-mass separation Rc.m. is 3.498(3) A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458320
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  • 2
    Electronic Resource
    Electronic Resource
    New measurements of microwave transitions in the water dimer (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6290-6299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: New measurements of ten K=1 lines, including six Q type and four R type, were made on the completely protonated species of the water dimer. For some of these lines, as well as for some K=0 transitions known from the literature, Stark coefficients were determined, and these Stark coefficients provide a confirmation of the assignments. The new K=1 measurements show that the splitting associated with the (HF)2-like tunneling motion decreases from about 19.5 GHz for K=0 to about 16.2 GHz for K=1. To understand the fact that K=1 lines are populated in our 1 K beam, we must assume, in accordance with the results of beam studies on other molecules, that levels of different nuclear spin modification relax separately. In an attempt to gain information on tunneling splittings other than that caused by the (HF)2-like motion, we have made new measurements on 1–0 and 2–1 transitions with K=0 for several partially deuterated species, in which the (HF)2-like motion cannot occur. Small splittings ranging from 4 to 145 MHz were observed. Because of the nature of the tunneling motions involved, these new data yield only the difference of the tunneling splitting in the upper and lower states of the transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453458
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  • 3
    Electronic Resource
    Electronic Resource
    The torsional–rotational spectrum and structure of the formaldehyde dimer (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 891-898 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectra of (H2CO)2 and (D2CO)2 have been observed with a pulsed beam, Fabry–Perot cavity, Fourier transform microwave spectrometer. Both species exhibit a-type spectra which are split by internal rotation of each monomer unit and an interchange of donor–acceptor bonding roles analogous to the water dimer. Rotational analysis of each spectrum provides the constants A=18583.(54) MHz, 1/2 (B+C)=3272.105(34) MHz, and B−C=503.92(17) MHz for (H2 CO)2 and A=14 862.1(35) MHz, 1/2 (B+C)=3030.2366(37) MHz, and B−C=490.977(18) MHz for (D2CO)2. Stark effect measurements result in derived electric dipole components μa =0.858(4) D and μb=0.027(10) D for (H2 CO)2 and μa =0.908(4) D and μb=0.095(4) D for (D2CO)2. The geometry obtained from fitting the derived moments of inertia has the planes of the two monomer units perpendicular in a nearly antiparallel orientation of the CO groups with a center-of-mass distance of 3.046(17) A(ring). The shortest carbon to oxygen distance (2.98 A(ring)) and hydrogen to oxygen distance (2.18 A(ring)) between the monomer units are indicative of a dual bond interaction to form a ring structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458123
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  • 4
    Electronic Resource
    Electronic Resource
    Microwave electric-resonance optothermal spectroscopy of (H2O)2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6077-6085 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of (H2O)2 has been measured between 14 and 110 GHz using a newly developed electric-resonance optothermal spectrometer (EROS) described here. The reported measurements extend previous results on the a-type Ka=0–0 and 1–1 bands for the A±2 , B±2 , and E± rotational-tunneling states and include the first observations of the c-type Ka =1–0 band for the A±2 and B±2 states and the a-type Ka =0–0 band for the A±1 states. For the A±1 states an interconversion tunneling splitting of 22.6 GHz is obtained, compared to the 19.5 GHz value found previously for the Ka =0 A±2 and B±2 states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456373
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  • 5
    Electronic Resource
    Electronic Resource
    The hyperfine structure of (DCCD)2 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8850-8863 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An experimental and theoretical study of the quadrupole-coupling hyperfine structure of the nonrigid (C2D2)2 dimer is carried out. This dimer exhibits a large amplitude interconversion motion which splits rotational levels into three sublevels. The quadrupole-coupling hyperfine pattern arising from the four deuterium atoms depends on the symmetry species of the tunneling sublevel. For nondegenerate sublevels, the hyperfine structure is especially interesting since the dimer behaves as if the quadrupole coupling were identical for all four deuterium atoms and the effective hyperfine Hamiltonian is completely symmetrical. The symmetry group used to classify the hyperfine levels is, therefore, the permutation group of four objects S4. For the other tunneling sublevels, which are doubly degenerate, the dimer behaves as if the two monomer units were inequivalent. Prior to the diagonalization of the hyperfine Hamiltonian, symmetry-adapted nuclear spin wave functions in S4 are set up and allow us to select hyperfine levels whose symmetry is compatible with the tunneling symmetry species. This formalism is used to analyze the hyperfine patterns of three rovibrational transitions in (C2D2)2, which were recorded under high resolution. The components of effective quadrupole-coupling tensors are thereby determined. These tensors are related to the eQq of an isolated DCCD monomer to obtain vibrationally averaged angles for large amplitude bending motions within the dimer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463360
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