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  • 1995-1999  (12)
  • 1
    Electronic Resource
    Electronic Resource
    Microwave spectrum and molecular structure of the dihydrophosphoryl radical H2PO in the X˜ 2A′ ground electronic state (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3450-3457 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dihydrophosphoryl radical H2PO in the X˜ 2A′ ground electronic state was studied by microwave spectroscopy using a source-modulated spectrometer combined with a free-space cell. The radical was generated by dc-glow discharge in a mixture of PH3 and CO2 and spectral lines of H2PO were observed in the 140–380 GHz region. The spectral pattern, including hyperfine structure, suggests that the radical has a pyramidal structure with Cs symmetry. About 1000 spectral lines of H2P16O and 250 lines of H2P18O were measured for the fine and hyperfine structures of rotational transitions up to N=10−9. Nineteen molecular constants including the hyperfine coupling constants of the phosphorus and hydrogen nuclei were precisely determined by a least-squares fit of the observed lines. Molecular structural parameters were derived from the rotational constants: r(PO)=1.4875(4) A(ring), r(PH)=1.4287(14) A(ring), (angle)HPO=115.52(10)°, and (angle)HPH=102.56(14)° with three standard deviations in parentheses. The PO bond is intermediate between the normal single and double PO bonds. The spin density of unpaired electrons was ascertained from the hyperfine coupling constants for the P and H atoms and is consistent with the molecular structure determined. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472534
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  • 2
    Electronic Resource
    Electronic Resource
    The microwave spectrum of the CD2 radical (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2167-2171 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The pure rotational spectrum of the CD2 radical in the X˜ 3B1 ground state was observed in the frequency region of 257 GHz–526 GHz by using a frequency modulated submillimeter-wave spectrometer. The CD2 radical was generated by the dc glow discharge of deuterated ketene, CD2CO. Twenty one fine and hyperfine component lines of four rotational transitions were measured and were analyzed by a least-square method. Rotational and fine-structure constants were revised in higher accuracy than those of the previous laser magnetic resonance (LMR) study. The hyperfine coupling constants for the deuterium nuclei have been determined for the first time. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470972
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  • 3
    Electronic Resource
    Electronic Resource
    Microwave spectroscopic detection of transition metal hydroxides: CuOH and AgOH (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11109-11112 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Pure rotational spectra of transition metal hydroxides have been reported. Millimeter wave spectra of CuOH and AgOH were recorded in a direct current discharge absorption cell in the range of 200–390 GHz. The spectra of both molecules correspond to that of a near prolate asymmetric top and only a-type R branch transitions were observed. The rotational and centrifugal distortion constants of CuOH and AgOH were precisely determined. Centrifugal distortion terms up to N2Nz10 were required to fit the observed line frequencies of 63CuOH. A preliminary analysis showed that AgOH is also strongly bent like CuOH with a bond angle smaller by about 2°. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479051
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  • 4
    Electronic Resource
    Electronic Resource
    Microwave spectroscopic detection of a transient phosphorus-bearing molecule, H3PO (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 912-917 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of the transient phosphine oxide, H3PO, was detected in the gas phase for the first time using a source-modulated spectrometer. The H3PO molecule was generated in a free space cell by a dc glow discharge of a mixture of PH3, CO2, and H2 gases and the corresponding spectral lines for each rotational transition of H3PO formed a pattern clearly indicative of a symmetric top molecule. Isotopomers of H3PO, i.e., H3P18O and D3PO were also produced; H3P18O in the same fashion as for H3PO, and D3PO, in a mixture of D2 and CO2 gases passing over red phosphorus grains. In total, 54 spectral lines of H3PO, 55 lines of H3P18O, and 61 lines of D3PO were measured for the fine structure of rotational transitions, J=2–1 to 12–11. The rotational constant, B0, and centrifugal constants, DJ, DJK, and HKJ were ascertained by a least squares analysis of the measured frequencies for each of the species. Using the rotational constants of the three isotopic species, the following r0 structure was determined: r0 (PO)=1.4763 Å, r0(PH)=1.4406 Å, and (angle)HPO=114.26°. The value of each structural parameter deviates significantly from the most recent results predicted by ab initio calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478058
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  • 5
    Electronic Resource
    Electronic Resource
    Submillimeter-wave spectrum of the AsH2 radical in the 2B1 ground electronic state (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 5351-5355 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The pure rotational spectrum of the AsH2 radical in its 2B1 ground electronic state was observed for the first time by microwave spectroscopy. The AsH2 radical was generated in a free-space cell by dc-glow discharge of a mixture of H2 and O2 gases over arsenic powder. Fifty-five fine and hyperfine components of six rotational transitions were measured in the frequency region of 304–374 GHz, and were analyzed by least-squares methods. Molecular constants, including the rotational constants, the centrifugal distortion constants, the spin-rotation coupling constant incorporating the centrifugal distortion term, and the hyperfine coupling constants associated with the arsenic and hydrogen nuclei, were precisely determined. The bonding in AsH2 was discussed on the basis of the hyperfine coupling constants, first determined in the present study. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477153
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental determination of the ground-state inversion splitting in D3O+ by microwave spectroscopy (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 5707-5709 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Inversion–rotation transitions of the fully deuterated hydronium ion, D3O+, were observed for the first time by microwave spectroscopy. The ion was generated in a hollow cathode cell by dc-glow discharge of a mixture of D2O and D2. Twenty six P- and Q-branch transitions were measured precisely for the lowest pair levels of inversion motion in the frequency region of 220–565 GHz. The ground-state inversion splitting and effective molecular constants for the upper and lower levels were determined by a least-squares fit of the measured line frequencies. The inversion splitting was determined to be 15.355 504 4(45) cm−1, where the number in parentheses denotes three standard deviations of the fit. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477191
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  • 7
    Electronic Resource
    Electronic Resource
    A new phosphorus bearing derivative of the methyl radical, CH2CP, studied by microwave spectroscopy and ab initio calculation (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4252-4257 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of the CH2CP radical in its 2B1 ground electronic state was detected for the first time using a source-modulated microwave spectrometer. The radical was generated in the cell by a dc-glow discharge in a mixture of PH3 and C2H2. Fine structure was observed but no hyperfine structure pertaining to the phosphorus and hydrogen nuclei could be resolved. In total 110 spectral lines were measured for the K-structure and fine structure of eight rotational transitions in the 300–380 GHz region. The rotational, centrifugal distortion, and spin-rotation coupling constants were obtained by a least-squares analysis of the measured frequencies. On the basis of accompanying coupled cluster calculations an accurate equilibrium structure could be established; re(CH)=1.0816(5) Å, αe(HCH)=118.22(5)°, R1e(CC)=1.3418(10) Å, and R2e(CP)=1.5889(10) Å. The equilibrium dipole moment is predicted to be μe=−1.15 D, with the negative end at the phosphorus site. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477030
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  • 8
    Electronic Resource
    Electronic Resource
    Microwave spectroscopic detection of HCCP in the X 3Σ− electronic state: Phospho-carbene, phospho-allene, or phosphorene? (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 1301-1307 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Microwave spectrum of the HCCP radical was detected for the first time in the X 3Σ− ground electronic state using a source-modulated microwave spectrometer. In total, 24 rotational transitions of HCCP in the 90–360 GHz region, 9 rotational transitions of DCCP in the 260–360 GHz range, and 24 rotational transitions of H13C13CP between 130–360 GHz were measured. Hyperfine structure pertaining to the phosphorus and hydrogen nuclei was observed for HCCP, and in the case of H13C13CP, only for phosphorus. The corresponding hyperfine coupling constants were ascertained in addition to the rotational, centrifugal distortion, and fine structure constants by a least-squares analysis of the measured frequencies. From the hyperfine coupling constants determined, the spin density of unpaired electrons was estimated to be 76% for the phosphorus atom and 42% for the carbon adjacent to the hydrogen. The r0 structure of HCCP was established from the rotational constants of HCCP and its isotopically substituted species: r0(CP)=1.685 Å, r0(CC)=1.241 Å, and r0(CH)=1.057 Å. These structural features are consistent with a linear phospho-allenic form that has been somewhat modified by a phosphorene. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474488
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  • 9
    Electronic Resource
    Electronic Resource
    The microwave spectrum of the NHD radical in the ground electronic state, 2A′′ (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9289-9296 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microwave spectrum of the monodeuterated species of NH2, NHD(X˜ 2A′′), was observed in the millimeter- and submillimeter-wave region. The NHD radical was produced by a dc-glow discharge through a NH3 and D2 mixture at around 220 K. Ten rotational transitions with both b- and a-type selection rules were observed in the 177–517 GHz region. The most important rotational transitions for astronomical observations, 101–000 and 110–101, were included and their detailed fine and hyperfine components were measured with high precision. The hyperfine interaction of the nitrogen, hydrogen, and deuterium nuclei, which are similar in magnitude, caused complicated hyperfine patterns and made their assignment relatively difficult. A least-squares analysis of the measured frequencies resulted in the determination of 40 molecular constants including nuclear spin–rotation coupling constants of N, H, D and, furthermore, nonaxial components of magnetic dipolar terms of H and D. The necessity of a higher K-dependent term of the dipole–dipole interaction constant for the hydrogen nucleus relative to the principal axis system reflects the effective geometrical change of the rotational levels. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475224
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  • 10
    Electronic Resource
    Electronic Resource
    Chemical Characterization of Melanins in Sheep Wool and Human Hair (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 9 (1996), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The color of hair and wool in mammals and feathers in birds is mostly determined by the quantity and quality of melanins that are synthesized in follicular melanocytes and transferred to keratinocytes. There are two chemically distinct types of melanin pigments: the black to brown eumelanins and the yellow to reddish pheomelanins. Melanins in sheep wool and human hair of various colors were characterized by HPLC methods to estimate 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-derived units in eumelanins and benzothiazine units in pheomelanins. Melanins were also characterized by spectrophotometric methods after differential solubilization in alkalies. It was demonstrated that 1) black wool in Asiatic sheep contains eumelanin with the DHICA content similar to black mouse melanin, while black to brown melanins from human hair contain much lower ratios of DHICA-derived units, comparable to the slaty mutation in mice, 2) dark brown to brown hair in human contains eumelanin whose chemical properties are indistinguishable from those of black hair, 3) dark red wool and red human hair contain pheomelanic pigments whose chemical properties are rather different from those of yellow pheomelanins in mice, and 4) light brown, blonde, and red hairs in human can be differentiated from each other with this methodology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0749.1996.tb00088.x
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