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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6408-6419 
    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).
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3476-3487 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction between the ethynyl radical, C2H (X 2Σ+), and methylacetylene (X 1A1′), which yields ethynylallene, pentadiyne, and butadiyne, has been studied at the density functional (B3LYP/6-311+G**) and coupled cluster (coupled-cluster single double perturbative triple/cc-pVTZ) levels of theory. These results agree with data from crossed molecular beam experiments where ethynylallene (10) and pentadiyne (13) have been observed. The C2H(1) radical initially attacks the π system of methylacetylene (2) without an entrance barrier to form Z-1-ethynylpropen-2-yl (3) or Z-2-ethynylpropen-1-yl (4) in highly exothermic reactions. Geometric considerations as well as the computed enthalpies suggest Z-1-ethynylpropen-2-yl (3) to be the dominant initial intermediate. Assuming single collision conditions as found in cold molecular clouds in the interstellar medium and distinct planetary atmospheres, numerous rearrangements may ensue the initial reaction step before ejection of a hydrogen atom or a methyl group releases the accumulated reaction energy. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1759-1762 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present the experimental set up of a microwave Fourier-transform spectrometer for the entire K band from 18 to 26.4 GHz. It is hereby shown that this type of spectroscopy is achieved above 18 GHz. Advantages and disadvantages are discussed. The performance is illustrated by the recordings of rotational transitions of various molecules.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 967-971 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of phenol(H2O) has been recorded using a pulsed molecular beam Fourier transform microwave spectrometer. Twenty a-type transitions have been observed and assigned. All a-type transitions are doublets with splittings varying from 1.13 to 4.01 MHz. These splittings are interpreted to result from the internal rotation of the water molecule. The ground state of this torsional motion is split into two levels with different spin statistical weights. Both torsional levels are treated independently as asymmetric rotor states. The resulting rotational constants are A=4291.486 MHz, B=1092.1484 MHz, and C=873.7263 MHz for the lower torsional level (σ=0) and A=4281.748 MHz, B=1092.329 55 MHz, and C=873.906 81 MHz for the upper level (σ=1). A fit of the molecular structure is performed by optimizing the intermolecular OO distance and two angles, describing the H-bonding arrangement. The resulting trans-linear structure is in reasonable agreement with the ab initio calculations © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2878-2880 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the use of piezoresistive cantilevers with an atomic force microscope that operates in conjunction with a scanning electron microscope. This is a very attractive combination because the two microscopes complement each other in terms of depth and lateral resolution, field of view, speed, and ability to image insulating surfaces. Images of a grating and an integrated circuit are shown as examples. Simultaneous operation in real time was achieved. © 1994 American Institute of Physics.
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs samples with a 100-nm-Co overlayer that had been subjected to rapid thermal annealing for 60 s at temperatures of 400–650 °C were analyzed using mass and energy dispersive recoil spectrometry. Separate characterizations of C, O, Co, Ga, and As depth distributions were performed. Both Ga and As had migrated to the surface at anneal temperatures higher than 450 °C. In a sample annealed at 650 °C, a clear enrichment of Ga in the outer 35 nm was observed. The composition for various depth intervals was determined for different temperatures. From Arrhenius plots, apparent activation energies were estimated to be about 0.6 eV for phase formation and 1.3 eV for diffusion. X-ray diffraction indicated that CoGa and CoAs phases were present in all the annealed samples. Scanning electron microscopy showed the surface to be reticulated after heat treatment, with grain growth at higher temperatures.
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 38 (1997), S. 3347-3357 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: We study local variations of causal curves in a space-time with respect to b-length (or generalized affine parameter length). In a convex normal neighbourhood, causal curves of maximal metric length are geodesics. Using variational arguments, we show that causal curves of minimal b-length in sufficiently small globally hyperbolic sets are geodesics. As an application we obtain a generalization of a theorem by Schmidt, showing that the cluster curve of a partially future imprisoned, future inextendible and future b-incomplete curve must be a null geodesic. We give examples which illustrate that the cluster curve does not have to be closed or incomplete. The theory of variations developed in this work provides a starting point for a Morse theory of b-length. © 1997 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 4072-4084 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design, performance, and operation of a broadband (3–26.5 GHz) high resolution microwave spectrometer is described. In comparison to previously developed molecular beam Fabry–Perot resonator spectrometers the design presented here implements some significant improvements: a coaxially oriented beam resonator arrangement (COBRA) formed by a confocal pair of mirrors incorporating an electromechanical valve and employing two pairs of microwave antennas, and a multioctave Fourier-transform microwave (FTMW) instrument providing the pulsed excitation source with microwave pulse phase-inversion scheme and the low-noise receiving system employing image-rejection downconversion with superheterodyne as well as quadrature detection. The entire apparatus, fully automated for scanning operation, covers a frequency range of more than three octaves. The novel design of the FTMW instrument does not require any changes of the spectrometer hardware in order to reach all regions of its spectral range. While operated in high resolution mode the COBRA-FTMW spectrometer is achieving a linewidth (half-width at half-height, HWHH) relative to the molecular emission frequency of better than 10−7 HWHH. The sensitivity and resolution of the spectrometer is demonstrated by several examples. © 1996 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3694-3699 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present hardware and software details of the pulsed molecular beam microwave Fourier transform (MB-MWFT) spectrometer used in the Kiel microwave group. We emphasize an automatic scanning facility which greatly increases the efficiency of MB-MWFT spectroscopy for the measurement of unassigned spectra.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 940-943 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The spectral transmittance and reflectance of an optical component, especially one with an interference coating, is severely dependent on angle of incidence and polarization. We report here on the design of an instrument which provides accurate, direct measurement of the spectral response of coated components at arbitrary angles of incidence.
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