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  • 1
    Electronic Resource
    Electronic Resource
    UV photodissociation and photodesorption of adsorbed molecules. 1. Methyl bromide on lithium fluoride(001) (1984)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 88 (1984), S. 6100-6103 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150669a009
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  • 2
    Electronic Resource
    Electronic Resource
    Superlattice excitons and optical absorption (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7369-7378 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A formalism based on the superlattice crystal coordinate representation, which is valid for arbitrary well and barrier widths, is developed and applied to the Wannier exciton problem. A simple model for the electron-hole Coulomb interaction within the independent subband approximation permits nonvariational calculation of exciton binding energies, oscillator strengths, and optical absorption of both bound and continuum exciton states. The effects of growth axis directed electric and magnetic fields are emphasized. Numerical results for GaAs/ Ga1−xAlxAs and In1−xGaxAs/GaAs exciton binding energies and oscillator strengths as functions of well width, barrier width, and electric and magnetic field strengths show excellent agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355005
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of SixGe1−x/Si heterostructures for device applications using spectroscopic ellipsometry (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 586-595 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic ellipsometry (SE) characterization of several complex SixGe1−x/Si heterostructures prepared for device fabrication, including structures for heterojunction bipolar transistors (HBT), p- and n-type heterostructure modulation-doped field-effect transistors, has been performed. It is shown that SE can simultaneously determine all active layer thicknesses, SixGe1−x compositions, and the oxide overlayer thickness, with only a general knowledge of the structure topology needed a priori. The characterization of HBT material includes the SE analysis of a SixGe1−x layer deeply buried (600 nm) under the silicon emitter and cap layers. In the SE analysis of n-type heterostructures, a silicon layer under tensile strain was examined. It was found that an excellent fit can be obtained using optical constants of unstrained silicon to represent the strained silicon conduction layer. SE was also used to measure lateral sample homogeneity, providing quantitative identification of the inhomogeneous layer. Surface overlayers resulting from prior sample processing were also detected and measured quantitatively. These results should allow SE to be used extensively as a nondestructive means of characterizing SixGe1−x/Si heterostructures prior to device fabrication and testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355271
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  • 4
    Electronic Resource
    Electronic Resource
    Photochemistry of adsorbed molecules. V. Ultraviolet photodissociation of OCS on LiF(001) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3645-3658 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dynamical studies of the UV photochemistry of submonolayer coverages of OCS physisorbed on 116 K LiF(001) are presented. Following pulsed ultraviolet laser irradiation (λ 222 nm), translational energy and angular distributions were obtained for photolysis products by angle-resolved time-of-flight mass spectrometry. Photolysis of adsorbates gave rise to distributions which differed markedly from gas phase photodissociation. Energetic sulphur and CO fragments were detected for coverages ≥10−5 monolayers. The cross section for photolysis in the adsorbed state was enhanced 103–104× relative to the gas phase. The dynamics for these photoprocesses were found to vary with adsorbate coverage, indicative of a catalytic influence of the surface on the photochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458795
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemistry of adsorbed molecules. VII. Ultraviolet photoejection and photodesorption of OCS on LiF(001) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3673-3684 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The UV photoejection and photodesorption of OCS on LiF(001) at 222 nm are reported. Translational energy and angular distributions were obtained by angle-resolved TOF mass spectrometry. Energetic photoejection (PEJ) product, characterized by a peak translational energy T'p∼0.3 eV, was detected for (approximately-greater-than)0.5 ML coverages of OCS(ad). The PEJ angular distribution was sharply peaked around the surface normal, ∼cos 18θ. The initial absorption of energy was into the chromophore of an OCS molecule. Molecular photodesorption (PDES) product, characterized by low translational energy, was detected for coverages ≥10−2 ML. The translational energy distribution P(T') was found to be a sensitive function of detection angle, adsorbate coverage and laser energy. Peak translational energies and FWHM's were ∼0.05 and ∼0.20 eV, respectively. Angular distributions were also sensitive to coverage, narrowing from ∼cos θ to cos 11θ with increasing coverage. Photodesorption is thought to involve absorption of radiation by defect centers in the LiF(001), with conversion of the absorbed energy into phonons which, following propagation to the surface, induce desorption of OCS(ad).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458797
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  • 6
    Electronic Resource
    Electronic Resource
    Photochemistry of adsorbed molecules. IV. Photodissociation, photoreaction, photoejection, and photodesorption of H2S on LiF(001) (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1498-1523 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The UV surface-aligned photochemistry (SAP) of submonolayers of H2S physisorbed on LiF(001) has been examined. Translational energy and angular distributions for photodissociation products and for H2S molecules leaving the surface after pulsed laser irradiation at 193 and 222 nm were measured by angularly resolved TOF to a quadrupole mass spectrometer. Single photon surface-aligned photodissociation (PDIS) of adsorbed H2S produced H with structured translational energy distributions P(ET) indicative of vibrational excitation within the complementary SH fragments. The SH vibrational distribution was bimodal and varied markedly with H2S coverage. Photoreaction (PRXN) within the adsorbate layer occurred as the H2S coverage increased beyond ∼0.1 monolayer. Molecular hydrogen was produced by PRXN of H with adjacent H2S(ad) molecules. The product H2 translational energy distribution showed evidence of both direct and indirect PRXN dynamics. At coverages greater than one monolayer, photoejection (PEJ) of H2S molecules with translational energies up to several eV was observed; PEJ was thought to be due to interadsorbate quenching of electronically excited H2S. At all the coverages examined, absorption of UV by the LiF substrate was found to photodesorb (PDES) H2S molecules with low translational energies (0–0.5 eV). The PDES was ascribed to an acoustic wave produced by laser excitation of color centers in the LiF, which were seen to fluoresce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455716
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  • 7
    Electronic Resource
    Electronic Resource
    Photochemistry of adsorbed molecules. VI. Ultraviolet photoreaction of OCS on LiF(001) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3659-3672 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The surface-aligned photoreaction (PRXN) of OCS physisorbed on LiF(001) was investigated at 222 nm. Ultraviolet PRXN within the adsorbate was detected over a wide range of coverages. Diatomic sulphur was produced by reaction of photolytically generated sulphur atoms with a coadsorbed OCS molecule: S*, S+OCS(ad)→S*2, S2(g)+CO(ad/g). Translational energy and angular distributions of the S2 reaction product were obtained by angle-resolved time-of-flight mass spectrometry. The dynamics of PRXN were found to vary with adsorbate coverage. At low coverages (〈10−2 ML), reaction was attributed to a "direct'' abstraction mechanism, leading to energetic S2. As the coverage was increased above 10−2 ML, both "direct'' and "indirect'' PRXN dynamics were observed. Possible origins of these differing photoreaction dynamics are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458796
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  • 8
    Electronic Resource
    Electronic Resource
    Photochemistry of adsorbed molecules. III. Photodissociation and photodesorption of CH3Br adsorbed on LiF(001) (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1475-1497 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Submonolayers of CH3Br physisorbed on a LiF(001) surface were irradiated by pulsed ultraviolet (UV) in ultrahigh vacuum in a study of surface aligned photochemistry (SAP). Translational energy and angular distributions were obtained for both photofragments and photodesorbed molecules by angularly resolved time of flight to a mass spectrometer. Single-photon adsorbate photolysis (PDIS) led to photofragment distributions, CH3 and Br, which differed from gas-phase photolysis. Photodesorption (PDES) of CH3Br was nonthermal and arose from UV absorption by the LiF crystal. The dynamics for these photoprocesses were found to vary in an informative way with the coverage and the phase of the adsorbed layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455148
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  • 9
    Electronic Resource
    Electronic Resource
    Experimental observation of filamentation growth in laser-produced plasmas (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2815-2824 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The filamentation instability has been observed and systematically studied in a low Z plasma under a variety of density gradients and electron temperatures. Growth lengths have been measured for several plasma conditions and as a function of the spatial size of the imposed intensity perturbation. The filamentation growth is compared to a model that assumes nonlocal electron energy transport and to ponderomotive theory. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871179
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  • 10
    Electronic Resource
    Electronic Resource
    Laser beam propagation and channel formation in underdense plasmas (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2825-2834 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results are presented which show the formation of density channels in a preformed plasma by a 100 ps laser beam focused with different f/number lenses. The density channels are diagnosed by an interferometer. The experiments are made with both line foci and circular foci up to intensities of 5×1016 W/cm2. The experimental channel size and density perturbation compare favorably with the predictions of two-dimensional theoretical models. The limited axial extent of the channels is shown to be due to the onset of the filamentation instability. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871180
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