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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4384-4388 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Solid phase epitaxy of amorphous SnxGe1−x films on strain relieved Ge films on Si(001) substrates was investigated for alloy compositions in the range 0.02≤x≤0.26. Films with compositions x〈0.05 crystallize by solid phase epitaxy as substitutional, strain relieved, diamond cubic alloys without phase separation or surface segregation of Sn. Films with higher Sn compositions exhibit more complicated behavior in which phase separation is believed to follow solid phase epitaxy. This sequence of transformations for higher Sn compositions yields epitaxial, substitutional, strain relieved, diamond cubic SnxGe1−x films with x∼0.05, and excess Sn is segregated in ∼100 nm size domains within the epitaxial alloy film. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4224-4236 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of the cyano radical (CN) with hydrogen was studied by time-resolved infrared absorption spectroscopy of individual rovibrational states of HCN. The initial vibrational level distribution of HCN(v10v3) was determined by plotting the time dependence of the fractional population of a vibrational level and extrapolating these curves to the origin of time. The experiments were carried out at two temperatures, 293 and 324 K, with similar results. It was estimated that about 50% of the available reaction exothermicity was deposited as vibrational excitation of the HCN product. Surprisingly, the HCN(101) vibrational level received a significant fraction of the observed vibrational population, implying that the CN vibration was not really a spectator bond in the reaction dynamics. Furthermore, the observed HCN(v10v3) vibrations only account for about 27% of the initial HCN population produced in the title reaction. A significant fraction of the product HCN molecules must have been produced with the bending mode excited, likely in combination with the H–C stretch vibrations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 6689-6699 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of the reactions of translationally energetic H atoms with BrCN, ClCN, and (CN)2 was studied by determining both the rotational state distribution and the translational energy disposition of the CN product ground vibrational level. The reaction was carried out using H atoms with a most probable translational energy of 92 kJ mol−1. The CN radical was monitored by time- and frequency-resolved absorption spectroscopy using the CN red system (A 2Π←X 2Σ) (2,0) band near 790 nm. Sub-Doppler resolution spectroscopy was used to determine the initial translational temperature of the CN(0,J) product. The fraction of the available reaction exothermicity that appeared as CN(0) rotational energy, fR, for H+XCN→HX+CN was 0.034±0.006, 0.061±0.02, and 0.13±0.007, for X=Br, Cl, and CN, respectively. Likewise, the fraction of the available reaction exothermicity that appeared as relative product translational energy, fT, was 0.52±0.25, 0.52±0.20, and 0.59±0.05, for X=Br, Cl, and CN, respectively. The absolute reaction cross sections for the H+XCN→HX+CN reactions were also measured to be 0.03, 0.02, and 0.3×10−16 cm2 for X=Br, Cl, and CN, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The integrated-absorption coefficients of several hyperfine lines of the magnetic dipole allowed transition of the bromine atom, Br, center at 3685.2 cm−1 were measured, and a value for the square of the magnetic dipole transition moment of the Br atom was determined. A theoretical calculation for the magnetic dipole transition moment was also carried out using a relativistic ab initio atomic structure formulation. The theoretical value was in excellent agreement with the value predicted assuming pure LS coupling, and in reasonable agreement with experiment. The Br atom was generated in equal concentration with the cyano radical (CN) by the 193 nm photolysis of cyanogen bromine, BrCN. The CN radicals were titrated by the rapid reaction with C3H8 to generate HCN and a small amount of HNC. Both time-resolved and frequency-scanned infrared absorption spectroscopy were used to monitor the Br, HCN, and HNC species. The photolysis of BrCN at 193 nm produced both the ground state Br(2P3/2) and the spin-orbit excited Br(2P1/2) atoms, and the yield for the production of Br(2P1/2) atoms was measured to be 0.31±0.01. The rate constants for the quenching of Br(2P1/2) by BrCN and C3H8 at 293 K were also determined. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6312-6319 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The square of the electronic–vibrational transition moment for the (2,0) band of the cyano radical (CN), A 2Π←X 2Σ+, red system at 789.5 nm has been determined using a direct time-resolved absorption technique. The line strength of the R1(8.5) transition of 12C14N was measured by comparison to the known line strength of the H12C14N(001)←(000) P(8) infrared υ3 fundamental transition near 3.05 μm. The CN radical was created by pulsed-laser photolysis of cyanogen, (CN)2, in a mixture of H2 and (CN)2 in either Ar or He carrier gas at 293 K. Both CN and HCN were monitored by time-resolved absorption spectroscopy during the same photolysis laser pulse. A simple kinetic model was used to relate the two absorption features to each other. The square of the electronic–vibrational transition moment for the A←X(2,0) band was found to be 7.8±1.0×10−38 esu2 cm2 in good agreement with theoretical calculations based on ab initio quantum chemistry methods. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4249-4253 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The flash method including the single- and double-ended method has gained widespread acceptance for measuring thermal diffusivity of thick foils (in millimeters) as well as thin films (in microns). However when the method is employed, some basic experimental conditions are assumed. In this paper, two of the assumptions, the finite absorption depth effect and the nonlinearity of the detector, are discussed in the situation of thin film samples. For the first one, the deviation of the factor ω1/2 (=π2αt1/2/L2) from 1.37 and the corresponding errors in deriving thermal diffusivity from t1/2 are discussed for various relative absorption depth δ. The result indicates criteria for the method to be available, that is, L(approximately-greater-than)10δ and L(approximately-greater-than)14δ for the double- and the single-ended method. For the second one, by considering the errors in voltage output of a (Hg, Cd)Te IR detector, how the factor ω1/2 deviates from 1.37 and the corresponding errors in thermal diffusivity measurement under various initial temperature conditions are discussed. The results are shown graphically and tabulated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3749-3752 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transient laser pulse has been used to generate nonsynchronous change of temperature rise and thermal expansion in thin films. The transient process of thermal expansion is recorded by a photoelectric high-speed acquisition system. By comparison of the calculated temperature rise and thermal expansion, thermal stress relaxation processes in Al films of 20–50 μm thickness is obtained. This result shows that, for transient heating, thermal stress exists even in the case of uniform temperature distribution and free expansion. And also there is a transient high stress in thin films under high-speed heating.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4215-4223 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The feasability of selective and complete population transfer between atomic or molecular levels by stimulated Raman scattering with delayed pulses involving spectrally broad light with characteristics typical for pulsed lasers is investigated. In extension of previous work, the effect on the transfer efficiency of phase fluctuations and of the detuning ΔR of the laser frequencies from the two-photon resonance is analyzed. The minimum pulse energy Pmin required to achieve a transfer efficiency of nearly unity is derived analytically, with some restrictions imposed on the type of phase fluctuations. Pmin increases approximately proportional to the square of the bandwidth of the laser radiation and to the square of ΔR. The conclusions are confirmed by the results of extensive numerical calculations. These studies also reveal a high sensitivity of the transfer efficiency to the autocorrelation of the fluctuating light.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8819-8829 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants for inelastic processes in Na2 (v,j)–Ne, Ar, Na collisions are determined at a mean collision energy of the order of 1 meV in a supersonic seeded beam arrangement. The initial vibrational state v and rotational state j is varied in the range 4≤v≤35 and 5≤j≤25. The Na2 molecules are excited by Franck–Condon pumping near the transition region to free molecular flow and the flux of molecules which survive in the level (v,j) is monitored far downstream behind a small aperture. It is shown that elastic processes do not contribute to the observed signal. The magnitude of the cross section for the sum of all inelastic processes is as large as several hundred A(ring)2. It is found that the vibrational motion of the molecule, which carries an energy of up to 500 meV, strongly influences the collision dynamics. The rate constant increases with v by about 35% within the range of vibrational levels studied here. Some state-to-state rate constants are also reported. The experimental results are in good agreement with data from quasiclassical trajectory calculations on a semiempirical bond-distance-dependent potential surface. The observations can be rationalized by realizing that the long range attraction increases with vibrational excitation since the polarizability of the molecule increases. Furthermore, the vibrational excitation in combination with the relatively long interaction time due to the low collision energy enhances the probability for a change of the initial quantum state of the molecule.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9472-9475 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The variation of the total integral cross section for the chemiluminescent channel with the vibrational excitation 3≤v‘≤19 is investigated using laser-induced fluorescence or coherent population transfer, a new method employing delayed interaction with two cw lasers to populate vibrationally excited levels. The cross section increases with v‘ by about 0.76% per vibrational level. The results are in agreement with the results of phase-space calculations, as well as with those from simple curve crossing models.
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