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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 10393-10394 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The resonance-enhanced multiphoton electron detachment spectrum of C5− was measured. The peaks observed at 470–500 nm were assigned to be 1 photon excitation of 2Πu to the 2Πg state. The vibrational structure gives the symmetric stretching frequency of ν2=718±43 cm−1 for the excited state of C5−. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3314-3317 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of hydrogenation on the structural change and magnetic properties of the Laves-phase GdFe2 compound has been investigated. Crystalline c-GdFe2 absorbs 4.4 hydrogen atoms per formula unit without any change in the crystal structure below 423 K. On the other hand, GdFe2 transforms to amorphous a-GdFe2H3.6 by hydrogenation from 423 to 523 K, where the decomposition of GdFe2 into GdH2 and α-Fe is prevented. The same amount of hydrogen (3.6 atoms per formula unit) dissolves in amorphous alloys produced by both hydrogenation and rapid quenching. Hydrogenation sharply reduces the Curie temperature of the crystalline alloy from 818 to 107 K, in contrast to the Curie temperature of 443 K for the hydrogen-induced amorphous alloy. The temperature dependence of the magnetization of the hydrogen-induced amorphous alloy is identical to that of the hydrogenated rapidly quenched amorphous alloy, suggesting similarity of their structures. The magnetization of the hydrogen-induced amorphous alloy shows a broad peak around 300 K. Above 300 K the magnetization of the amorphous alloys is largely uninfluenced by hydrogen. Below the peak it is reduced by hydrogenation.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 778-782 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Cyanoacetylene underwent polymerization reaction in a solid phase at pressures above 1.5 GPa. The Raman study of the reaction product showed that the polymer had a conjugated linear backbone with CN pendant groups. The Raman spectra for this substituted polyacetylene demonstrated a resonance behavior similar to that reported for trans-polyacetylene. The optical gap associated with the π–π* transition in the conjugated system was smaller than that of trans-polyacetylene, probably due to the resonance interactions between the CN triple bonds and the conjugated double bonds.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4565-4568 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Raman spectra were measured for liquid (0–0.7 GPa), crystalline cubic (0.7–0.9 GPa), and orthorhombic (0.9–3.5 GPa) phases in C2H2 at room temperature. For the orthorhombic phase, the high-pressure behavior of the librational and internal vibrations was obtained in a wide pressure range. The frequencies of all the librational modes increased monotonically with pressure, while those of the internal modes showed a variety of frequency shifts depending on vibrational mode. These high-pressure data will be of great use for the construction of theoretical models for the intermolecular interactions in crystalline C2H2.
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  • 5
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2814-2817 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: At room temperature, cyanoacetylene undergoes a liquid–solid transition at 70±30 MPa and further a polymerization reaction at 1.5 GPa. Raman spectra indicates that the crystal structure of the high-pressure phase is isomorphic with the monoclinic low-temperature structure (P21/m, Z=2), in which linear cyanoacetylene molecules are joined with CH NC hydrogen bonds to form infinite one-dimensional chains. The internal stretching frequency of the C–H proton donor decreases wtih increasing pressure, while that of the C 3/4 N proton acceptor increases. The librational modes associated with the rotational motions of the rigid molecules show large shifts to higher frequencies with pressure. The observed frequency shifts are attributed to the strengthening of the CH⋅⋅⋅NC hydrogen bond in the one-dimensional molecular chain.
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  • 6
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 529-534 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The mechanism and kinetics of the pressure-induced polymerization of acetylene were studied by Raman spectroscopy. The polymerization reaction occurred in the orthorhombic phase at room temperature and pressures above 3.5 GPa. Dominant formation of trans-polyacetylene suggested that the monomer underwent trans opening of the triple bond and polymerized along the diagonal of the bc plane of the unit cell. The reaction was described as an idealized one-step and one-dimensional growth process by an Avrami equation with an exponent 1.34.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1334-1335 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A new doping method named molecular layer doping (MLD) is proposed. MLD is based on surface chemical adsorption of dissolvements from induced dopant gas molecules. Ultrashallow boron-doped layers are successfully achieved by MLD using B2 H6 gas. The p+ n junction formed by MLD exhibits excellent characteristics, with a reverse bias leakage current of less than 2.5×10−16 A/μm2 at 5 V. MLD is attractive in that it offers high-density, shallow-junction, damage-free, selective doping in a short time.
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  • 8
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1277-1279 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A new mechanism for self-generated current oscillations in modulation-doped semiconductor heterostructures under parallel conduction is proposed. It is based upon the nonlinear dynamics of real-space electron transfer and delayed dielectric relaxation of the interface potential barrier resulting from the space charge in the doped AlGaAs layer. From our simulations we predict current oscillations in the 20–80 GHz range under dc bias.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 2122-2123 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The hydrogen-induced transformation from the crystalline to the amorphous state in GdFe2 has been studied by means of differential thermal analysis. GdFe2 absorbs hydrogen in the crystalline state above 420 K by an exothermic reaction. The resultant crystalline c-GdFe2H3.8 alloy transforms to the amorphous a-GdFe2H2.8 alloy above 470 K exothermally, which crystallizes to the stable phases α-Fe and GdH2 above about 700 K. The driving force for the hydrogen-induced transformation is suggested to be the difference in the enthalpy resulting from the different hydrogen occupation sites in both states of alloy.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1037-1039 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A mixture of elemental powders of Ti and Zr, which exhibit the complete solid solubility, has been mechanically alloyed by a high-energy ball mill, at room temperature, under a controlled nitrogen atmosphere. The products were characterized by x-ray diffraction, transmission electron microscopy, differential scanning calorimetry, and chemical analysis. Nanocrystalline fcc type c-TiZrN0.9 powders were prepared by MA in 2 MPa of nitrogen gas. On the contrary, amorphous a-TiZrN0.3 alloy powders were synthesized by MA in 0.04 MPa of nitrogen gas.
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