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  • American Institute of Physics (AIP)  (20)
  • American Association for the Advancement of Science (AAAS)
  • 1985-1989  (22)
  • 1
    Electronic Resource
    Electronic Resource
    Field-induced magnetic anisotropy in a dilute dispersion of γ Fe2O3 particles (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1691-1693 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The application of an alternating field (AF) of 60-mT peak to an isotropic sample containing dilutely dispersed particles of γFe2O3 from magnetic tape causes it to become magnetically anisotropic. The anisotropy of initial susceptibility so produced can be described by an oblate ellipsoid of revolution with the unique axis aligned with the AF direction. A consequence of this effect is that an isothermal remanent magnetization (IRM) is then more easily acquired if the direct field is applied perpendicular to the previously applied AF direction than if it is applied parallel to this direction. The anisotropy of IRM acquisition at direct fields between 20 and 40 mT is an order of magnitude greater than the anisotropy of initial susceptibility and is 40% of the maximum possible value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339903
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of silicides by rapid thermal annealing over polycrystalline silicon (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 631-634 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the formation of titanium silicide by rapid thermal annealing in nitrogen and argon ambients over polycrystalline silicon. A sheet resistance of about 3 Ω per square for a 300-A(ring) Ti layer was achieved after 900 °C/10-s annealing treatment, which decreased to about 2 Ω per square after 1100 °C/10-s treatment. The silicides were found to be stable during rapid thermal annealing up to 1100 °C/10 s with no or negligible migration of titanium along the grain boundaries in polycrystalline silicon. An external layer (titanium rich, mixture of titanium oxide and nitride) was observed to form during rapid thermal annealing treatment in the nitrogen ambient, but the surface remained clean in the argon ambient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337404
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  • 3
    Electronic Resource
    Electronic Resource
    Population lifetimes of OH(v=1) and OD(v=1) stretching vibrations of alcohols and silanols in dilute solution (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5004-5018 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Picosecond infrared pump–probe experiments determined the vibrational population lifetimes (T1) of the hydroxyl fundamental stretching mode OH(v=1) in 12 alcohols (R3COH) and 8 silanols (R3SiOH) in dilute room temperature CCl4 solutions. T1 for the silanols is in the range 185〈T1〈292 ps, while T1 for the alcohols is much less (T1〈80 ps). The deuterium-exchanged analogs (COD and SiOD) exhibit population relaxation times similar to protonated hydroxyls. An analysis of the vibrational energy levels corresponding to modes involving the four bonds nearest the hydroxyl groups of these molecules is used to qualitatively explain the trends of the observed T1 lifetimes for these systems. Solution T1 lifetimes are also compared to those previously measured for OH(v=1) on the surface of silica and in other condensed-phase, room temperature systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451690
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  • 4
    Electronic Resource
    Electronic Resource
    Vibrational predissociation of the nitric oxide dimer: Total energy distribution in the fragments (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2333-2334 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational, spin-orbit, lambda doublet, and kinetic energy distributions were measured by laser-excited fluorescence techniques for the nitric oxide fragments formed from the vibrational predissociation of nitric oxide dimers in a free jet expansion. The NO fragments, produced following excitation in the dimer ν1 fundamental, were described by a rotational "temperature'' of TR(approximately-equal-to)100 K, with full equilibration of lambda doublet states, and approximately equal populations in the two spin-orbit states. The velocity distributions were isotropic with an average fragment kinetic energy of 400 cm−1. Time-resolved measurements placed a 15 ns upper limit on the predissociation lifetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451082
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  • 5
    Electronic Resource
    Electronic Resource
    Energy distribution in the nitric oxide fragments from the ν7 vibrational predissociation of NO–C2H4 (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5286-5288 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational level distribution of the NO fragments formed as a result of the predissociation of the vibrationally excited NO–C2H4 (ν7) van der Waals molecule was measured by laser excited fluorescence techniques. The distribution was found to be Boltzmann in character, described by the rotational temperature 75±15 K. An average kinetic energy release of ≈105 cm−1 per fragment, in an isotropic flux distribution, was determined from Doppler profiles of the NO fragments in selected rotational levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448604
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  • 6
    Electronic Resource
    Electronic Resource
    Time-resolved measurements of OH(v=1) vibrational relaxation on SiO2 surfaces: Isotope and temperature dependence (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 2361-2364 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Picosecond infrared spectroscopy was used to measure the vibrational energy relaxation time T1 of OH(v=1) and OD(v=1) groups chemisorbed on silica surfaces over the temperature range 100≤T≤800 K. The observed T1 times and their temperature dependencies are discussed in terms of a multiphonon relaxation mechanism. Limiting low temperature lifetimes are T1=220±20 ps (1σ) for OH(v=1) and T1=149±10 ps for OD(v=1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450350
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  • 7
    Electronic Resource
    Electronic Resource
    Infrared multiphoton dissociation of methyl nitrite in a molecular beam: Internal states of the nitric oxide fragment (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 2236-2239 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational-, spin-, and lambda doublet-state distributions for nitric oxide (NO) formed in the CO2 laser multiphoton dissociation of methyl nitrite, CH3ONO, in a pulsed molecular beam are reported. Upon methyl nitrite photolysis by temporal square wave infrared laser pulses at 983 cm−1 of 50 ns duration and 800 MW/cm2 intensity, the low-lying rotational levels of the nitric oxide fragments formed in the 2Π1/2 (F1) and 2Π3/2 (F2) spin-orbit states exhibited Boltzmann-like population distributions, characterizable by the rotational temperatures TR (F1)=400±10 K and TR (F2)=530±100 K; the integrated populations for J〈30.5 of the two spin components were in the ratio F1/F2=2.7 : 1. For those highly rotationally excited levels with J(approximately-greater-than)24.5 there is no measurable spin preference, the level population depending solely on total internal energy Eint. There is no apparent preference for formation of either lambda doublet component and there is no observable fragment alignment, the nascent NO species exhibiting an isotropic distribution of angular momentum vectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448317
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  • 8
    Electronic Resource
    Electronic Resource
    Vibrational deactivation of surface OH chemisorbed on SiO2: Solvent effects (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5216-5231 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Picosecond infrared transmission spectroscopy was used to directly measure the vibrational energy relaxation time T1 of hydroxyl groups chemisorbed on the surface of colloidal silica (SiO2). T1 was obtained for OH(νstretch=1) in the strongly bound "isolated sites'' of fumed silica particles in vacuum and dispersed in several liquids at T=293 K. At the SiO2/vacuum interface, T1=204±20 ps. When the SiO2 particles are surrounded by solvents, the relaxation time of the surface OH(v=1) groups decreases: for the liquids CCl4, CF2Br2, CH2Cl2, and C6H6, T1(ps)=159±16, 140±30, 102±20, and 87±30, respectively. T1 does not depend on the size of the SiO2 particles for the range 70 A(ring)≤ diameter ≤150 A(ring), or on the surface OH coverage up to an average density of 4 OH/100 A(ring)2. Significant amounts of physisorbed water (5 H2O/100 A(ring)2) decreased T1 for the isolated OH(v=1) to T1=56±10 ps. For comparison to the surface hydroxyls, the vibrational deactivation time for OH(v=1) groups in the bulk of fused silica (OH/SiO2≈130 ppm by weight) was determined to be T1=109±11 ps. These observations are discussed in terms of the possible mechanisms of vibrational energy flow in these systems. The observed T1 values demonstrate that the spectral linewidths (e.g., IR and Raman) observed for these surface vibrations are too large (by factors of 200–2000) to be caused solely by T1 uncertainty broadening. The slow transfer of vibrational energy between surface and lattice vibrations may have important implications for surface chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448646
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  • 9
    Electronic Resource
    Electronic Resource
    Picosecond measurements of the dissociation rates of the nitric oxide dimer v1=1 and v4=1 levels (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 6235-6237 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Direct picosecond measurements of the vibrational predissociation rates of the nitric oxide dimer excited to v=1 levels of the symmetric (ν1=1870 cm−1) and antisymmetric (ν4=1789 cm−1) N–O stretching fundamentals are reported. Lifetimes obtained are 880±260 ps for ν1 and 39±8 ps for ν4 excitations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451494
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  • 10
    Electronic Resource
    Electronic Resource
    Time resolved studies of vibrational relaxation dynamics of CO(v=1) on metal particle surfaces (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4619-4620 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational relaxation dynamics of CO chemisorbed on small Pt and Rh particles supported on SiO2 has been investigated by picosecond time-resolved infrared transient bleaching experiments. A vibrational T1 lifetime of ≈7 ps has been observed for several different samples, independent of polarization, pump intensity, and sample temperature from 100–400 K. A 1:3 isotopic dilution has no effect upon T1. This T1 lifetime is a factor of 10–50 times shorter than T1 reported for metal carbonyl cluster compounds in solution and on SiO2 supports. Two possible mechanisms are considered to account for the rapid T1 decay; redistribution of the energy throughout the broad CO vibrational band, and relaxation directly to electron–hole pairs in the metal particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456598
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