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  • American Institute of Physics (AIP)  (26)
  • 2015-2019  (5)
  • 1985-1989  (21)
  • 1
    Electronic Resource
    Electronic Resource
    Magnon Brillouin scattering in FeSi sputtered films (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4968-4970 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally excited spin waves in sputtered FeSi films (2.6 wt. % of Si) have been studied at room temperature by Brillouin scattering in external magnetic fields of up to 4.0 kOe. Scattering from the Damon–Eshbach surface mode and the standing spin waves has been observed. The magnetic constants of the FeSi films are determined as follows: γ/2π =2.87±0.06 GHz/kOe, g=2.05±0.04, 4πMs=19.9±0.4 kG, 4πMb=20.1±0.4 kG, and Db=1.18±0.24×10−9 Oe cm2. Here, the subscripts s and b refer to surface and bulk, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343219
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  • 2
    Electronic Resource
    Electronic Resource
    Brillouin scattering from spin waves in sputtered Co-Zr films (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 328-335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally excited spin waves in thin Co91-Zr9 sputtered films have been studied at room temperature by Brillouin scattering in external magnetic fields of up to 3.5 kOe. In order to precisely determine the g factor and the surface exchange constant, we extensively studied the Damon–Eshbach mode in a 1-μm-thick film. From the slope of the surface magnon frequency in an external magnetic field, the g factor of 2.17±0.04 is determined. The surface exchange stiffness constant Ds has been determined by examining the surface wave-vector dependence on the surface magnon frequency. We obtained a value of Ds =6.9±2.0×10−9 Oe cm2. The best way to determine the bulk stiffness constant is to observe the standing spin waves excited in a thin film whose thickness is less than 200 nm. We could observe scattering from the standing spin waves of up to a third order in a film of 85±5 nm thick. The bulk exchange stiffness constant Db of 2.2±0.4×10−9 Oe cm2 is obtained from the external field dependence of the standing spin-wave frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343878
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  • 3
    Electronic Resource
    Electronic Resource
    Dependence of coercivity on the anisotropy field in the Nd2Fe14B-type sintered magnets (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3559-3561 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the coercivity (HcI)of Nd15(Fe1−xCox)77B8 and (Nd1−xDyx)15Fe77B8 sintered magnets and that of the saturation magnetization (Ms) and the anisotropy field (HA) of Nd2(Fe1−xCox)14B and (Nd1−xDyx)2Fe14B single crystals have been observed in the temperature range between 295 and 800 K. The dependence of the coercivity on the major magnetic properties of the matrix phase in the Nd-Fe-B based magnets are investigated using the μ0HA vs μ0HcI+Ms plot. It is demonstrated that this method of analysis is useful in studying the coercivity mechanism of the Nd-Fe-B based sintered magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338725
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  • 4
    Electronic Resource
    Electronic Resource
    Dissolution pits and Si epitaxial regrowth in the Al/(111)Si system (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4499-4502 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reaction between an Al film and a (111) single-crystal Si has been studied by microscopic observation. Dissolution pits were formed on the Si surface due to dissolution of Si into the Al film, by annealing above 300 °C. The shapes of the pits were triangular or hexagonal shaped with a flat bottom. Each side of the pits was parallel to the 〈110〉 directions of the substrate. At the dissolution pits, triangular or hexagonal Si islands regrew epitaxially to the substrate in the Al film. A mechanism for the formation of the dissolution pits and Si epitaxial regrowth is proposed in relation to the strain fields affected by the strain centers in the Si substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341276
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetization and magnetic anisotropy of R2Co14B and Nd2(Fe1−x Cox)14B measured on single crystals (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3571-3573 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization and anisotropy field of R2Co14B with R being La, Nd, and Gd and of Nd2(Fe1−xCox)14B have been measured on single-crystal specimens. The cobalt sublattice has a planar anisotropy: K1=−1.30 MJ/m3 at 4.2 K for La2Co14B with the [110] direction being the room-temperature easy direction of magnetization. The rare-earth ions in R2Co14B experience a smaller exchange field than in R2Fe14B, which results in a rapid reduction of the rare-earth sublattice magnetization and anisotropy with increasing temperature. Because of the planar anisotropy of cobalt and the weaker R-Co interactions than R-Fe, the anisotropy field of Nd2(Fe1−xCox)14B turns out to be almost independent of the cobalt concentration in a temperature range between 300 and 500 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338729
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  • 6
    Electronic Resource
    Electronic Resource
    Theory of quantum beats in time-resolved multiphoton ionization of molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1501-1510 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An expression for the probability of time-resolved three-photon ionization via coherently excited resonant states of a molecular system is derived in the perturbative density matrix formalism with the aid of the Liouville space Feynman diagram. It is shown how the time evolution of the molecular coherence in the first resonant state can be detected as a function of the delay time between the pumping and probing lasers through the probing two-photon ionization process. The three-photon ionization process consists of the simultaneous and sequential processes which are classified by the Liouville space Feynman diagrams. The possibility of appearance of quantum beats in the pump–probe three-photon ionization is discussed by performing model calculations of the probability of ionization. The role of the direct and redistributed processes is discussed. The redistributed process is induced by intramolecular processes in the resonant state. The theoretical treatment is applied to the (1+2) three-photon ionization of pyrazine observed by Knee et al. It is demonstrated that the fast decay component (110 ps) of the pyrazine spectra originates from the intramolecular dephasing of the vibronic coherence created by the pumping pulse laser, and this component appears only when the redistributed process (the ionization process through triplet levels) is absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454128
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  • 7
    Electronic Resource
    Electronic Resource
    Application of the indirect dephasing model to resonance and dispersed fluorescence in the isolated molecular complex (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2510-2517 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The theory of indirect dephasing proposed by Hiroike is applied to studying the mechanism of line broadening in resonance and dispersed fluorescence spectra of molecular complexes in supersonic free jet. In the indirect dephasing model, the width of the luorescence spectra which is characterized by the homogeneous linewidth can be expressed in terms of two parameters, the rate of intramolecular vibrational redistribution (IVR), γ and frequency change induced by the IVR, δω. It is shown that the non-Markovian character introduced into the interaction between the intra- and intermolecular modes reduces the indirect dephasing rate. The theory is applied to calculation of the linewidth of the resonance fluorescence of the tetrazine–Ar molecular complex excited in 6a1 vibronic level. The introduction of the non-Markovian character is necessary to calculate the linewidth of the fluorescence in a molecular complex with a few intermolecular modes such as tetrazine–Ar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452103
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  • 8
    Electronic Resource
    Electronic Resource
    Theory of vibrational predissociation of van der Waals complex in the adiabatic approximation model (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 7106-7116 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory of the vibrational predissociation (VPD) of linear triatomic van der Waals (vdW) complexes in the adiabatic approximation model is developed aiming to evaluate the VPD rates from higher quantum states as well as the lowest one of the initially excited intramolecular vibrational mode. The adiabatic wave functions of the high frequency intramolecular mode and the adiabatic potential curves are constructed from a Morse-type interaction potential between the two neighboring atoms of the vdW bond. Using Fermi's Golden Rule, expressions for the rate of the VPD are derived both in the Condon approximation and in the non-Condon scheme. Important contribution of the non-Condon scheme in the adiabatic approximation model is demonstrated by performing model calculations of the VPD rate constants of I2X vdW complexes. The magnitudes of the rate constant in the Condon approximation are smaller than those in the non-Condon scheme by about one to two orders. It is shown that there is a good correspondence in the vibrational quantum number dependence between the treatment in the adiabatic approximation model and that in the scattering theory based on the zero-order diabatic basis set derived by Beswick and Jortner, and that the magnitudes of the vibrational predissociation rate constant calculated by them exist between those in the Condon approximation and in the non-Condon scheme. An approximate expression for the potential displacements between two adiabatic potentials and that for the intramolecular frequency shifts are also derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451397
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  • 9
    Electronic Resource
    Electronic Resource
    Resonance Raman scattering from molecules with a nonequilibrium vibronic distribution (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 1246-1254 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Expressions for the differential cross section of the resonance Raman scattering from molecules in which initially prepared nonequilibrium vibronic levels undergo vibrational and/or electronic relaxations are derived by using the generating function method. Two kinds of the initial nonequilibrium vibronic distributions, single vibronic level and Poisson ones are taken into account. A displaced harmonic oscillator model for the initial and resonant vibrational states and a linear vibrational quantum number dependence of the relaxation constants are adopted in deriving the cross sections. Model calculations of the time-resolved resonance Raman scattering cross sections and of the excitation profiles of the nth order Stokes and anti-Stokes Raman bands are performed by using the derived expressions. The results of the calculation indicate that the anti-Stokes Raman bands make a significant contribution to the resonance Raman scattering from the nonequilibrium vibronic distributions. It is suggested that measurements of the excitation profiles are useful for analyzing the nonequilibrium distribution initially prepared and the subsequent relaxation mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448445
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  • 10
    Electronic Resource
    Electronic Resource
    Non-Markoffian theory of quantum beats in molecular fluorescence (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 2112-2119 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a theory of quantum beats in molecular fluorescence taking into account collision effects (such as pure dephasing due to elastic collision) without invoking the Markoff approximation. Model calculations of the time dependent fluorescence from molecules with two excited levels are performed in order to see how the non-Markoffian character in the collision process exerts influence upon the quantum beat pattern. It is suggested that if the pure dephasing between the excited states is a Markoffian "the degree of modulation of the beats'' decreases exponentially with time; if it is in the static limit the degree of modulation of the beats decreases as a Gaussian function (the non-Markoffian behavior in the quantum beats). A given case can be classified as either Markoffian or non-Markoffian, depending on the relative magnitudes of the collision duration time τc, the beat frequency ω, and the coupling strength v which is characteristic of the pure dephasing process. The Markoff approximation holds only if the condition ω〈v〈1/τc is satisfied; the non-Markoffian behavior appears in the quantum beat pattern when ω〉v, even if v2τ2c〈1 .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450422
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