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  • 1
    Electronic Resource
    Electronic Resource
    Submicrosecond switching with a Fabry–Perot interferometer containing a nematic liquid crystal (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6148-6154 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the temporal response of a biased Fabry–Perot etalon with a nematic liquid crystal exposed to short (∼10 μs) voltage pulses is presented. It is found that the finesse is the crucial factor determining the achievable switching time. For a given maximum transmission the reflectivities of the Fabry–Perot mirrors are optimized to achieve minimum switching times. In particular, switching times of 0.5 μs with an initial transmission of 3% and a maximum value of 70% have been obtained. The experimental results are in good agreement with theory. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363688
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  • 2
    Electronic Resource
    Electronic Resource
    Voltage dependence of microsecond switching in a nematic optical phase modulator (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3020-3025 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the temporal response of a biased planar nematic liquid crystal to short (∼10 μs) voltage pulses is presented. The resulting optical phase shift varies quadratically with time during the first 2 μs after switching the voltage on and then linearly. A theoretical model is developped starting from the Leslie-Ericksen theory which describes the investigated phase modulation in the microsecond time scale. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360052
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  • 3
    Electronic Resource
    Electronic Resource
    Initial vibrational level distribution of HCN[X˜ 1Σ+(v10v3)] from the CN(X 2Σ+)+H2→HCN+H reaction (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4224-4236 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.477028
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental and theoretical determination of the magnetic dipole transition moment for the Br(4p5)(2P1/2←2P3/2) fine-structure transition and the quantum yield of Br(2P1/2) from the 193 nm photolysis of BrCN (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7821-7831 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.478689
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental measurement of the transition moment for the (2,0) band of the CN A 2Π←X 2Σ+ red system at 789.5 nm (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6312-6319 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.477273
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  • 6
    Electronic Resource
    Electronic Resource
    The initial vibrational state distribution of HCN X˜ 1Σ+(v1,0,v3) from the reaction CN(2Σ+)+C2H6→HCN+C2H5 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 7966-7982 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of the cyano radical (CN) with ethane was studied using time-resolved infrared absorption spectroscopy to monitor individual rovibrational states of the HCN product. A method is described that can be used to determine the initial vibrational state distribution at pressures of several Torr. This technique was applied to the title reaction to determine that the vibrational states of HCN(v1,0,v3), where v1, v3=0, 1, and 2, were not directly populated in the title reaction to any significant extent. The initial vibrational energy content of the CN radical was also varied but did not influence the initial population in the HCN vibrational levels probed in this experiment. The time dependence of HCN(v1,0,v3) was followed and interpreted in terms of bimolecular rate constants for vibrational relaxation with ethane. The title reaction is mode specific in its energy disposal in that at least every HCN product appears to have at least one quantum of bending excitation, likely in combination with stretching vibrations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468995
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  • 7
    Electronic Resource
    Electronic Resource
    Direct measurement of the transition dipole moment of the v3 asymmetric C–H stretching vibration of the CH3 radical (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2863-2872 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A direct measurement of the transition dipole moment, μ3, of the degenerate v3 in-plane asymmetric C–H stretching vibration of the methyl radical has been made. The measurements were carried out in a flow reactor using laser-photolysis transient infrared absorption spectroscopy. Cyano (CN) radicals (and Cl atoms) were produced by laser photolysis of BrCN (or ClCN) at 193 nm and reacted with methane to give both CH3 and HCN (and HCl). The intensities of 18 rotational lines of the v3 fundamental band were measured relative to the R(8) line of the C–H stretching vibration (v3) of HCN(001←0). The best estimate of the transition dipole moment of the CH3 (00110←0) transition was provided by the measured line intensity for the CH3 (00110←0)rR(3,3) transition and was determined to be μ3=0.0327±0.0021 D. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470499
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  • 8
    Electronic Resource
    Electronic Resource
    Transvaginal ultrasound in the management of women with suspected cervical incompetence (1997)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 104 (1997), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1997.tb11474.x
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  • 9
    Electronic Resource
    Electronic Resource
    Apparatus to measure the shear modulus of Langmuir monolayers as functions of strain amplitude and frequency (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1792-1795 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have built an apparatus to study the viscoelastic response and measure the complex shear moduli of Langmuir monolayers as functions of the frequency and amplitude of the applied sinusoidal shear strain. A rotor is placed in contact with the monolayer and suspended by a torsion wire; a coil attached to the rotor carries a direct current. The voltage induced in this coil by a high-frequency external magnetic field is used to measure the angle of rotation with an accuracy of ∼0.005°. A low-frequency external magnetic field is used to drive the rotor into forced oscillations at the desired frequency (1 mHz–1 Hz), or the rotor may oscillate freely with the "natural" frequency variable over the range 0.01–3 Hz using a static external magnetic field. The apparatus has a large dynamic range for shear modulus measurement (∼5×10−3–103 dyn/cm), achieved by using the free oscillation (ring-down) method for films with low shear moduli (∼5×10−3–1 dyn/cm), and the forced oscillation method for films with higher shear moduli (∼1–103 dyn/cm). We have found that the complex shear modulus G of heneicosanoic acid Langmuir monolayers depends on the applied strain except at very low amplitudes. We also present sample data showing the frequency dependence of G. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147994
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  • 10
    Electronic Resource
    Electronic Resource
    Large (50 μm)2 metal–semiconductor–metal photodetectors with 18 GHz bandwidth at 3 V bias; Reduction of hole pileup (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 196-198 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal–semiconductor–metal photodetectors were fabricated on an AlGaAs/GaAs/AlGaAs double heterostructure with no graded layers. Devices with photolithographically defined finger spacing and width of 1 μm ("1×1") exhibited a saturation bandwidth of greater than 20 GHz, for bias voltages between 3 and 4 V. We attribute this to minimal hole pileup, and propose a simple model for the energy of hot holes near the band offset at the cathode. Using this model, estimates of the bias required to reduce hole pileup in different material systems were derived. The model shows good agreement with results reported here and elsewhere. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121753
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