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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical studies on the femtosecond real-time measurement of ultrafast electronic decay in polyatomic molecules (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7184-7194 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a computer simulation of the real-time detection of ultrafast electronic decay dynamics in polyatomic molecules with femtosecond laser pulses. The intramolecular non-Born-Oppenheimer quantum dynamics is treated numerically exactly for a two-state three-mode vibronic coupling model representing the conically intersecting S1 and S2 excited states of pyrazine. The pump–probe signal is evaluated in lowest order perturbation theory with respect to the radiation–matter interaction by numerical integration over the pump and probe pulses. We discuss in some detail the dependence of the pump–probe signal on the properties of the laser pulses (frequencies and pulse durations). The calculations predict a dramatic (∼12 000 cm−1) and ultrafast (∼20 fs) red shift of the stimulated-emission signal as well as distinctive quantum beats in the pump–probe signal as a function of the delay time. Both effects are very pronounced and should therefore be relatively easily detectable experimentally. They are expected to be generic features of ultrafast internal-conversion processes in polyatomic molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456248
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  • 2
    Electronic Resource
    Electronic Resource
    Surface chemistry of CuxS and CuxS/CdS determined from x-ray photoelectron spectroscopy (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 5056-5065 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy spectra measured on copper sulfide (CuxS) films showed that a thin surface reaction product containing Cu in the +2 valence state was formed on CuxS films exposed to air for 46 h at 40 °C and 90% relative humidity. An entirely different CuxS surface reaction product layer was formed in dry air at 170 °C for 30 min and it contained sulfur in the +6 valence state. The copper (Cu) valence state in CuxS was not found to be +2 even when the x value was less than 1.9. When the argon sputter-cleaned surface of CuxS or CuxS/CdS films was exposed to room-temperature air for 10 min, cadmium (Cd) atoms appeared on the CuxS surface. X-ray powder diffraction patterns showed that CuO and CdS reacted at 500 °C in flowing nitrogen to form Cu2S and CdO. This cation exchange between CdS and copper oxide may explain the surface Cd on the CuxS films. The standard free energy of reaction between CuO and CdS is positive while that between Cu2O and CdS is negative. These results indicate a method for stabilizing CuxS/CdS solar cells against degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335283
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  • 3
    Electronic Resource
    Electronic Resource
    Resolution of the Thomson spectrometer (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1-5 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The resolution of Thomson spectrometers is examined. Charge, mass energy, and momentum resolutions are found as functions of collimation parameters and field strengths. The results are generally applicable to all Thomson spectrometer systems. In conjunction with this analysis, a compact Thomson spectrometer with high resolving power is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335389
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  • 4
    Electronic Resource
    Electronic Resource
    Monolayer abruptness in highly strained InAsxP1−x/InP quantum well interfaces (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1142-1144 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InAsxP1−x/InP strained quantum well structures have been prepared by atmospheric-pressure organometallic vapor phase epitaxy (OMVPE). Structures with compositions of x=0.40–0.67 and quantum well thicknesses of 0.8–16 nm were evaluated using photoluminescence spectroscopy. Strain in the pseudomorphic wells ranged from 1.3 to 2.1%. Doublets and multiplets are observed in the photoluminescence spectra and are attributed to luminescence from regions in the wells differing in thickness by a single monolayer, with atomically smooth interfaces over areas greater in lateral extent than the exciton diameter. Typical full widths at half maximum of the photoluminescence from the thinnest wells are 8–14 meV, comparable to the best reported values for thin lattice-matched quantum wells prepared from the InGaAs(P)/InP system using OMVPE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100742
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  • 5
    Electronic Resource
    Electronic Resource
    Wave dispersion theory in a plasma column bounded by a cylindrical waveguide (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1108-1115 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A unified theory of the electromagnetic wave propagation in a plasma column immersed in an axial magnetic field is developed, including the important influence of finite geometrical effects on wave dispersion properties. The analysis is carried out within the framework of a macroscopic cold fluid model. Coupled eigenvalue equations for the electromagnetic perturbations are obtained for an arbitrary density profile. For a flat-top density, a closed algebraic dispersion relation of the electromagnetic wave is obtained without any prior approximation. This transcendental dispersion relation is analytically solved in special cases of (a) uniform plasma, (b) infinite magnetic field, (c) zero magnetic field, (d) electrostatic perturbations, and (e) the low-frequency whistlerlike mode. In order to demonstrate the important influence of finite geometrical effects, the low-frequency whistlerlike mode is rigorously investigated for axisymmetric waves in a completely filled waveguide. From the analysis, it is shown that the whistlerlike mode propagates in the axial direction only when the total electron line density exceeds a critical line density. Moreover, the conventional dispersion relation of the low-frequency whistler mode is recovered only for a large plasma radius. Otherwise, the plasma geometrical effects play a pivotal role in wave propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341869
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  • 6
    Electronic Resource
    Electronic Resource
    Propagation of a mildly relativistic electron beam at sub-Torr pressures (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 4119-4126 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This report presents observations on propagation of a mildly relativistic electron beam (γ=2.4) in several different gases (air, He, N2, and Ar) at low pressure (10–320 mTorr). At such low pressures, and with beam currents of several kiloamperes, beam-induced ionization may result in self-focusing of an electron beam. Beams propagating under this condition are said to be in the ion-focusing regime of propagation. The injected beam has an rms radius of 0.7 cm and a transverse temperature of 35 keV. Beam transport efficiency was measured for He, N2, and Ar. A simple calculation was performed to determine the space-charge neutralization fraction as a function of time. Using the results of this calculation, the charge-transport efficiency is found and compared with the experimentally measured quantity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337492
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  • 7
    Electronic Resource
    Electronic Resource
    Emittance meter for time-resolved electron-beam propagation studies (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 186-188 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple emittance meter is designed which is capable of measuring the temporal evolution of the emittance of a propagating electron beam. The design is based on that of a slit-pinhole emittance meter. A Cherenkov emitter is utilized as the electron detector. A streak camera is used to record the time-resolved optical Cherenkov radiation from the detector. Experimental results with a 700-keV, 4-kA, 100-ns electron beam are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140006
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  • 8
    Electronic Resource
    Electronic Resource
    Compact magnetic electron energy analyzer (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1534-1536 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact magnetic energy analyzer designed for the measurement of electron energies in the range from 20 keV through 1.5 MeV is described. The simple device, based on the semicircular focusing principle, is constructed from a high induction permanent magnet enclosed in a soft iron case. The design and operation of the analyzer in pulsed electron beam devices are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138520
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  • 9
    Electronic Resource
    Electronic Resource
    Simple time-resolving Thomson spectrometer (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 240-244 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a simple time-resolving Thomson spectrometer system which can provide the temporal information of ions produced by a pulsed source, in addition to the time-integrated information. The electric field in a conventional spectrometer is modulated by a time-varying field. It is shown that from the resulting spectrogram, the time-resolved quantities associated with the ions can be deduced. Experimental results with plasma focus produced ions are given as an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139314
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  • 10
    Electronic Resource
    Electronic Resource
    Transverse oscillations of an electron beam propagating in the ion focused regime (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3917-3919 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetic probe array is utilized to perform current centroid measurements of a 4 kA, 700 kV, 100 nsec electron beam propagating in the ion focused regime. Results with several filling gases all show transverse oscillation, which may be indicative of hose-type motions of the beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865782
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