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  • 1
    Electronic Resource
    Electronic Resource
    Overtone spectroscopy of methyl C–H stretch vibration in CH3CF2Cl and CH3CFCl2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4111-4117 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoacoustic spectra of the second (3νCH), third (4νCH), and fourth (5νCH) overtones of the methyl C–H stretches in CH3CF2Cl and CH3CFCl2 were measured. The spectra are characterized by a multiple peak structure of partially resolved triplets and quartets with an anomalous linewidth decrease in the 4νCH region. The results are interpreted in terms of a simplified local mode model for C–H stretching vibrations, including also the stretch-deformation Fermi resonances. The model accounts for most spectral features and allows determination of the time scale for vibrational redistribution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480959
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  • 2
    Electronic Resource
    Electronic Resource
    Vibrationally excited states of CH3CFCl2: Intramolecular vibrational redistribution and photodissociation dynamics (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 10787-10795 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Utilizing vibrationally mediated photodissociation of jet-cooled CH3CFCl2 enabled monitoring of the second (3νCH) and third (4νCH) overtones of the methyl in the ground electronic state. The excited molecules are photodissociated by ∼235 or 243.135 nm photons that further tag Cl(2P3/2)[Cl] and Cl(2P1/2)[Cl*] isotopes or H photofragments via mass selective (2+1) resonantly enhanced multiphoton ionization. The vibrational spectra are characterized by a multiple peak structure related to C–H stretches and to Fermi resonating levels involving the CH3 deformation. The cooling in the expansion reduces the rotational and vibrational congestion and affords a determination of the splittings and the upper limits for homogeneous broadening of the transitions. The highest-frequency peak of 4νCH exhibits an additional splitting, related to coupling of the mixed stretch–deformation states with other modes of the molecule. The yield of all three photofragments increases as a result of preexcitation, demonstrating that the energy is not preserved in the excited bond but rather flows to the C–Cl bond. The initial vibrational state preparation not only enhances C–Cl and C–H bond cleavage but also affects the Cl*/Cl branching ratio, as compared to the nearly isoenergetic one-photon 193 nm photolysis of vibrationless ground state CH3CFCl2, implying that it alters the photodissociation dynamics. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481752
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrogenation decomposition desorption recombination magnets based on Sm2+δ Fe17M0.4 carbonitrides (M=IVB/VB/VIB group elements) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6012-6014 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hydrogenation decomposition desorption recombination (HDDR) process is carried out to produce permanent magnets based on Sm2+δFe17M0.4 carbonitrides, where M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W; and δ≤0.6. It is found that minor additions of M significantly reduce the amounts of α-Fe and SmFe3 in the starting materials. The best isotropic HDDR magnet obtained is for M=Ti, which has an intrinsic coercivity of 18 kOe and an energy product of 9.8 MGOe at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355492
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  • 4
    Electronic Resource
    Electronic Resource
    Hall-effect study of an ion-bombarded polymer (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4202-4204 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an extended Hall-effect study of ion-bombarded poly(benzimididazobenzophenanthroline ladder), which resembles a disordered metal. We have investigated the dependence of carrier concentration and mobility on ion energy and sample temperature during bombardment and on measurement temperature. The dramatic increases in mobility and conductivity with bombardment energy and temperature indicate increased cross-link density. Concomitant slight decreases in carrier concentration may result from fewer defects in the cross-linked network. The mobility decreases slightly with measurement temperature while the conductivity is dominated by the gradually increasing carrier density. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363295
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  • 5
    Electronic Resource
    Electronic Resource
    Bulk anisotropic magnet of Sm2Fe17 type produced from the carbide by gas-solid reaction after sintering (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6559-6560 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bulk anisotropic magnets with the composition of Sm2(Fe,M)17CxNy (M=metal) have been produced by conventional powder sintering of the carbide, followed by gas-solid reaction. The results show that this is a very promising technique for producing high-performance bulk anisotropic magnets based on intercalated rare-earth–iron compounds. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363646
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  • 6
    Electronic Resource
    Electronic Resource
    Optical study on the size effects in BaTiO3 thin films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1392-1395 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To study the size effects in ferroelectric thin film, we measured the optical transmittance and Raman spectra in BaTiO3 thin films deposited by the rf-magnetron sputtering technique on fused quartz and (111) Si substrates. A variation in the energy gap and Raman peaks with film thickness and grain size was observed and the possible origin was analyzed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363875
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  • 7
    Electronic Resource
    Electronic Resource
    Light scattering in p-type GaAs:Ge (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2388-2395 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present in this work the results of a Raman spectroscopy study on the plasmon–phonon coupling in Ge-doped p-type gallium arsenide. A series of polarized Raman scattering experiments were carried out on epitaxial films grown by liquid-phase epitaxy on (100) GaAs substrates at 20, 100, and 300 K. The films were p type with free hole densities varying in the range of 5×1017–1×1020 cm−3. Under the scattering configurations employed, the longitudinal optical (LO) mode is forbidden for crossed polarization while the transverse optical (TO) mode is forbidden for both parallel and crossed polarizations. However, all the polarized Raman spectra showed two peaks with frequencies close to the TO and LO phonons of semi-insulating GaAs. The appearance of such forbidden modes was accounted for with a theoretical model which considers phonon–plasmon coupled modes with wave vectors much larger than those given by the regular q≈0 wave vector transferred by photons. Ionized acceptor impurities provide such additional wave vector transfer through elastic scattering of the photoexcited electrons and holes. It is demonstrated that the experimental values for position and linewidth of the peaks are well described by the theoretical calculations when Fröhlich-type and deformation potential mechanisms are considered as means of interaction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363074
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  • 8
    Electronic Resource
    Electronic Resource
    Optical and electrical properties of selectively delta-doped strained InxGa1−xAs/GaAs quantum wells (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2627-2632 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here an investigation of selectively delta-doped strained InGaAs/GaAs quantum wells. Electronic structures of the systems were calculated by self-consistently solving the Schrödinger and Poisson equations and the calculations revealed a systematic variation of the band structure as the delta sheet moved away from the center of the well to the edge and finally to the barrier. The results were found to be in agreement with our photoluminescence (PL) measurements. For center-doped samples, band-gap renormalization was found to be strong from the PL data, and our realistic random-phase approximation calculation for the heavily doped sample is in excellent agreement with the PL data. The radiative lifetimes were measured to be around 450 ps for all the samples, and surprisingly they vary very little from sample to sample although the wave-function overlap was considerably different for some samples. We also report Shubnikov–de Haas (SdH) measurements on the two barrier doped cases. For the heavily doped sample (A12132), two oscillation signals were detected and they were identified as two upper subbands. The measured electron densities were in very good agreement with the self-consistent calculation. Illumination did not make any difference to the measured densities. For the low-doped sample (A12025), however, the measured electron density before illumination is much smaller than the calculated, and illumination was found to make a large difference. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361133
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  • 9
    Electronic Resource
    Electronic Resource
    X-ray structural studies of nitrogen diffusion in Dy2Fe17 : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6038-6040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reaction between N2 and Dy2Fe17 has been studied by thermopiezic analysis on 20–25 μm sized powders in the temperature range 400–500 °C. Partially nitrided powders were analyzed using CuKα x-ray diffraction and thermomagnetic techniques. Both high angle x-ray and thermomagnetic data show only the presence of Dy2Fe17 and Dy2Fe17N3−δ (δ〈0.3) with no evidence of intermediate compositions. The results of the x-ray diffraction experiments at several Bragg peaks were simulated using a two phase model structure: a Dy2Fe17 core with a Dy2Fe17N3 surface layer. The results show that at low temperatures the nitride layer is too thin to account for all of the nitrogen absorbed by the sample, indicating that a significant amount of the nitrogen diffused into the core of the particles, presumably along grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358358
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of group IV B/V B/VI B additions on the magnetic properties of Sm2+δ Fe17 carbonitrides : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5997-5999 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Curie temperature, anisotropy field, and lattice constants are measured for the Sm2+δ Fe17M0.4 (δ≤0.6) carbonitrides for M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W. It is found that minor additions of M reduce the Curie temperature, with the largest decrease of 28 K for M=Mo, and that the fluctuations in Curie temperature are not related to the changes in unit cell volumes. Compared with Sm2+δ Fe17NxCy, most of the M additives reduce the anisotropy field with the largest decrease of about 10 kOe for M=Zr. The V addition has almost no effect on the anisotropy field and the Ti addition gives a 4–5 kOe enhancement of the anisotropy field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355487
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