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  • American Institute of Physics (AIP)  (428)
  • Cambridge University Press  (52)
  • American Physical Society (APS)
  • American Geophysical Union (AGU)
  • 1990-1994  (480)
  • 1
    Electronic Resource
    Electronic Resource
    High-power index-guided distributed out-coupled grating surface emitting laser-amplifiers with narrow spectra and high-quality beams (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 955-957 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Emission of a 100 mW cw beam into a nearly diffraction limited near-circular spot by a grating surface emitting (GSE) semiconductor laser, with radiance of 5.3×106 W/sr cm2, is described. The distributed out-coupled master oscillator power amplifier (DOC-MOPA) devices comprise active grating outcoupled power amplifiers and monolithic distributed feedback laser oscillators. With single wavelength (930 nm) operation demonstrated to 260 mW, they produce narrow linewidth (10 MHz) beams and near-ideal far-field patterns. The DOC-MOPA promises to become an efficient, compact source of high-quality ≥1 W cw light. Such fully collimated high power cw beams demonstrate the potential of GSE lasers to serve in systems requiring higher power than available from conventional edge-emitting technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108531
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  • 2
    Electronic Resource
    Electronic Resource
    A new electrochemical cell for atomic force microscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1019-1020 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Described is the design for a new electrochemical cell for in situ studies with the atomic force microscope. Improvements over presently used cells include an axially symmetric electrode geometry, large counter electrode, and the ability to incorporate a standard reference electrode close to the working electrode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145108
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  • 3
    Electronic Resource
    Electronic Resource
    Optical dephasing in solution: A line shape and resonance light scattering study of azulene in isopentane and cyclohexane (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5477-5484 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of a line shape and resonance light scattering study of the S1←S0 and S2←S0 electronic transitions of azulene in isopentane and cyclohexane are reported. The results are analyzed using two different non-Markovian master equations that make different assumptions about the statistical properties of the bath. For both these origin transitions we find that the solution dynamics fall in the so-called intermediate modulation regime. If exponential decay is assumed for the bath correlation function we obtain a correlation time of the bath of 25 fs for the S1←S0 transition and of 13 fs for the S2←S0 transition at room temperature. From the frequency dependence of the ratio of fluorescence to Raman yields of the S1←S0 transition we calculate an excited state lifetime of 1.4±0.2 ps using the parameters of the bath derived from the line shape analysis, and irrespective of which master equation is used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459617
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  • 4
    Electronic Resource
    Electronic Resource
    Fourier transform spectroscopy of C4H (butadiynyl) in Ar at 10 K: C–H and C≡C stretching modes (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1597-1603 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Fourier transform infrared (FTIR) isotopic study of the C4H (butadiynyl) radical produced by trapping the products from the vacuum ultraviolet photolysis of diacetylene (C4H2) and 1,3-butadiene (C4H6) in solid argon at 10 K has been carried out in the midinfrared from 400–3900 cm−1. A variety of carbon-13 and deuterium substituted C4H2 and C4H6 parent molecules were used to produce various isotopomers of C4H. On the basis of their isotopic behavior two absorptions at 3307.4 and 2083.9 cm−1 have been assigned to the ν1, C–H stretching and ν2, C 3/4 C stretching modes. The previous identification of the other C 3/4 C stretching mode, ν3=2060.6 cm−1, which was based on the effects of deuteration, has been confirmed and the corresponding frequencies for various 13C-substituted isotopomers have been measured. The following frequencies have been obtained for ν1, ν2, and ν3 for C4H isotopomers: 3307.2, 2078.9, and 2023.8 cm−1 for H–C 3/4 C–C 3/4 13C; 3307.2, 2069.9, and 2032.5 cm−1 for H–C 3/4 C–13C 3/4 C; 3307.2, 2066.8, and 2054.0 cm−1 for H–C 3/4 13C–C 3/4 C; 3293.3, 2048.9, and 2057.4 cm−1 for H–13C 3/4 C–C 3/4 C; 3292.5, 2050.6, and 2024.6 cm−1 for H–13C 3/4 C–C 3/4 13C; 3292.5, 2050.6, and 2030.0 cm−1 for H–13C 3/4 C–13C 3/4 C; 3306.3, 2063.3, and 2019.5 cm−1 for H–C 3/4 13C–C 3/4 13C; 3306.3, 2050.6, and 2018.0 cm−1 for H–C 3/4 13C–13C 3/4 C; 3290.1, 2007.9, and 1981.6 cm−1 for H–13C 3/4 13C–13C 3/4 13C; and 2579.3, 2056.5, and 2049.7 cm−1 for D–C 3/4 C–C 3/4 C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459138
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  • 5
    Electronic Resource
    Electronic Resource
    Percolation and diffusion in two-dimensional microporous media: Pillared clays (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3872-3880 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the adsorptive and diffusive properties of N2, H2O, and rare gas atoms (Ar and He) in the pillared layered silicate clay systems [Cr(en)3+3]x[Co(en)3+2−(en)]1−x−L, where L is vermiculite (V), fluorohectorite (FHT), or montmorillonite (M), and (en) is an ethylenediamine ligand. In these mixed ion intercalates the intercalated [Cr(en)3+3] cation, where all three en ligands are coordinated to chromium, represents a laterally small pillaring agent, whereas [Co(en)3+2−en] represents a laterally large, ligand-dissociated species. Such systems are excellent models for two-dimensional microporous media. Adsorption measurements were carried out for N2, H2O, and Ar and diffusion studies were performed using simulation methods for both Ar and He. We find that the adsorptive and diffusive properties depend sensitively on the size of the diffusing species and the concentrations x and (1−x) of the intercalants. For Ar adsorption in the FHT system we observe a percolative response when x reaches 0.79. Using simple geometrical models to describe these microporous media, along with computer simulation, we can understand the x=0.79 percolation threshold. In addition, simulation studies of the relative diffusion rates of He and Ar for x=0 and 1, and comparison of these rates with experimental measurements by Zhou and Solin, suggest that He diffusion near narrow constrictions may be strongly suppressed by quantum effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466376
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of guest–host interactions on the guest molecule in intercalated alumino-silicate compounds (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3346-3350 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have intercalated Cr(en)3+3 and Co(en)3+3 molecules (en=ethylenediamine), in known solid-solution fractional quantities, into the highly purified layered alumino-silicate fluorohectorite. Both molecules have like chemistry, but different physical sizes as they function to prop open the interlamellar gallery. As the fractional component x in [Co(en)3+3]x[Cr(en)3+3] 1−x–fluorohectorite is systematically varied, we observe the effect of intercalation on the host crystal basal spacing and the effects of intercalation on the guest molecules. Typical of the intercalation of rigid-layer compounds with agents differing in size, the basal spacing shows a sigmoidal dependence on fractional concentration. This is due to the large, but not infinite rigidity of the host and guest constituents. The lifetime of the fluorescence emission from the Cr(en)3+3 molecule exhibits the same sigmoidal dependence, indicating that the uniaxial stress exerted on the molecule, as it props open the gallery, is the primary factor dictating the guest fluorescence properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466426
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  • 7
    Electronic Resource
    Electronic Resource
    Far infrared laser magnetic resonance detection of CHD (X˜ 3A‘) (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8706-8712 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Far infrared laser magnetic resonance (FIR-LMR) spectra of the CHD radical in its X˜3A‘ electronic ground state were observed and assigned. The radicals were generated in the reaction of Na atoms with CHDBr2. LMR spectra were observed using seven laser lines at wavelengths around 100 to 200 μm. The spectra were assigned to six different rotational transitions and the molecular parameters of CHD were determined by a least squares fit. A number of additional transitions, observed using a laser line at λ=184.3 μm but not yet assigned in detail, were attributed to a coupling between the accidentally almost degenerate NKaKc=505 and 413 rotational levels induced by the εab term in the spin–rotation Hamiltonian and by the off-diagonal components of the hyperfine coupling tensor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466726
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  • 8
    Electronic Resource
    Electronic Resource
    On the quantum cross sections in dilute gases (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3813-3820 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The quantal cross section Q(N)qm for collision in dilute gases is given for any order N, where previously in the literature only values up to N=4 were to be found. The quantum-statistical character of Q(N)qm is discussed and calculations are presented for Q(1) through Q(6) for Boltzmann, Fermi–Dirac, and Bose–Einstein cases for 3He–4He, 3He–3He, and 4He–4He using extensive tables of phase shifts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466370
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  • 9
    Electronic Resource
    Electronic Resource
    Origin of turbulence-producing eddies in a channel flow (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1011-1022 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A principal theoretical problem in understanding wall turbulence is the determination of how turbulence is created and sustained, i.e., the explanation of how energy is transferred from the mean flow to the turbulence. Flow-oriented vortical eddies have been associated with large Reynolds stresses and with the production of turbulence in the viscous region close to the wall. Their creation and evolution are investigated in a high-resolution direct numerical simulation of turbulent flow in a channel. An important finding is that they regenerate themselves by a process that appears to be weakly dependent on the outer flow. This involves the enhancement of streamwise vorticity at the wall, of opposite sign, at a location where a stress-producing eddy lifts from the wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858666
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  • 10
    Electronic Resource
    Electronic Resource
    End effects for the falling cylinder viscometer (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 25-33 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results are presented for the Stokes velocity of a circular cylinder of radius a and length L moving axially through a viscous fluid contained within a coaxial closed cylindrical tube of radius b and length H. The results cover the intermediate range 0.21 ≤a/b≤0.70 and are found to be consistent with theoretical results for the narrow gap case (a(approximately-equal-to)b) and with previous experimental results for the wide gap case (a(very-much-less-than)b). The fractional difference between the observed drag and the theoretical drag is represented well by 1.67x−0.017, where x=(b−a)(a/b)1/2/L. The negative term is interpreted as representing an effective cylinder length of 0.983L, and the 1.67x term is interpreted qualitatively as a measure of the degree to which the fluid is displaced radially by the falling cylinder. The limitations of our expression for end effects are explored experimentally. Additional experimental results are presented for two cases in which the ends of the cylindrical tube are not closed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858781
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