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  • 11
    Electronic Resource
    Electronic Resource
    Hyperfine and Zeeman quantum beats in the B 2Π1/2 state of NO (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3968-3976 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum beat signals have been observed in v=0, 1, 2, and 3 of the B 2Π1/2 state of NO for the first time and are used to carry out Doppler free spectroscopy in these levels. Beat signals are observed at zero magnetic field in all four vibrational levels between different hyperfine components for J=3/2 and J=5/2, and are analyzed to derive accurate hyperfine constants and quadrupole coupling parameters. Although from their magnetic tuning rates the beats between the different hyperfine levels can be assigned to particular F'↔F separations, the energy ordering of the F levels and the parity assignment remain to be determined. Independently of this exact assignment a small variation in the hyperfine parameters with vibrational state is observed which is irregular in v=3 indicating the presence of an interaction with another electronic state. When a small magnetic field is applied much more intense beat signals are observed which occur between the Zeeman split components of a single hyperfine level. The B 2Π1/2 state is nominally nonmagnetic in the Hund's case (a) limit and so the effective g values vary rapidly with J due to spin–orbit uncoupling. The relative intensities of these beat signals and their variation with both magnetic field and vibrational level is accurately predicted using the known spectroscopic constants and a fitted value of gr. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468525
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  • 12
    Electronic Resource
    Electronic Resource
    A two-color (1+1′)+1 multiphoton ionization study of CS2 in the 61 000–65 600 cm−1 energy region (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4847-4854 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The (1+1′)+1 resonance enhanced multiphoton ionization (REMPI) spectrum of jet-cooled CS2 has been recorded in the 61 000–65 600 cm−1 excitation energy range. Four prominent band groups are observed that can be assigned to Δν2=−1 and Δν2=1 sequences of the two-photon electronically forbidden 4p 1,3Δu←X˜ 1Σ+g transitions. Weak bands to higher energy appear to be associated with the 310, 230 and 110210 bands and corresponding sequence bands. The results show that the upper states are not 3d Rydberg states as has been previously supposed, and are consistent with a recent reinvestigation of the corresponding (3+1) REMPI spectrum. Further experimental information is obtained on the anomalous vibrational band structure of transitions to the 3Δu state. The 201 and 212 bands of the 4p 1Πu←X˜ 1Σ+g transition are also observed, but are much weaker, suggesting that vibronic interactions are less important in this state compared to the 4p 1,3Δu states. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470620
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  • 13
    Electronic Resource
    Electronic Resource
    Disorder induced enhancement of the third order optical nonlinearity in a conjugated polymer (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2295-2301 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report on the relationship between material disorder and nonlinear optical response for a conjugated polymer. Inverse Raman scattering, the technique used here, is sensitive to the transition cross sections of both the purely electronic (Sv=01↔Sv=00) and vibronic (Sv=01↔Sv=10) transitions accessed, and both of these quantities are related to the extent of disorder in the polymer backbone. We have verified these morphology dependencies using crystalline and amorphous samples of the polydiacetylene poly(4BCMU). The magnitude of the nonlinear response per backbone repeat unit in the amorphous material is comparable to that of the crystalline form because of the large potential well displacement between the ground and excited electronic states characteristic of the disordered material. This increased potential well displacement compensates for the nonlinear response lost to the reduced macroscopic polymer alignment associated with the two-dimensionally isotropic spin cast film. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468717
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  • 14
    Electronic Resource
    Electronic Resource
    A study of some organic reactions using density functional theory (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2063-2079 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Twelve organic reactions (six closed shell and six radical) were studied using semiempirical, traditional ab initio and density functional methodologies. Full geometry optimizations of all species, both minima and transition states, were performed, and calculated geometries and barrier heights compared with experimental data. Our results demonstrate that although currently available density functionals tend to underestimate barrier heights, especially for radical reactions—in some cases reactions with low barriers are predicted to be essentially barrier free—they provide a significant improvement over standard methods. The adiabatic connection method recently proposed by Becke [J. Chem. Phys. 98, 5648 (1993)], in which a portion of the exact Hartree–Fock exchange is mixed in to the density functional, looks very promising. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468728
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  • 15
    Electronic Resource
    Electronic Resource
    First observation of the v=3 level of the B 1Σ+ Rydberg state of CO (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3956-3961 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new diffuse vuv band of 12C16O at 92 800 cm−1 has been observed in absorption and assigned to the B–X(3–0) transition. The assignment is based on the excellent agreement found between the observed band and a calculated spectrum of the B–X(3–0) transition, where a previously optimized two channel close-coupling model of the B 1Σ+–D' 1Σ+ Rydberg–valence predissociation interaction has been used to calculate the B(v=3) state molecular constants, J dependent predissociation widths and the J dependent B–X(3–0) vibronic transition moments. The relative absorption cross-section for this transition has also been calculated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468523
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  • 16
    Electronic Resource
    Electronic Resource
    The chemical potential in atomically inhomogeneous fluids in external force fields by computer simulation (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4098-4102 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The accuracy and practicality of the Widom fictitious-particle insertion method for determining the chemical potential is tested for very inhomogeneous fluids in strong external potentials by a series of molecular dynamics computer simulations. The chemical potential determined in this way is found, as predicted, on an atomic scale to be independent of position in the fluid to a few percent even when the density varies by up to a factor 80. This severe test means that this method of determining chemical potential is established as reliable and accurate in any well-found computer simulation even when the system is very inhomogeneous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467527
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  • 17
    Electronic Resource
    Electronic Resource
    The effect of grid quality and weight derivatives in density functional calculations (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 8894-8902 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Full density functional geometry optimizations on hydrogen peroxide and heptane/dimethyl pentane using six different numerical grids are presented. The grids vary in quality and gradients are calculated (1) assuming a fixed grid and no weight derivatives, and (2) with full allowance for a "moving'' atom-centered grid and inclusion of the weight derivatives. The results clearly demonstrate that accurate energies and geometries can be obtained with around 3500 points per atom for medium-sized systems (up to say 30 atoms) without the necessity of including the weight derivatives. The latter only begin to influence the results for grids which are of insufficient quality to guarantee reliable values in any case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468081
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  • 18
    Electronic Resource
    Electronic Resource
    The "Compact Toroid Injection Experiment" tomographic imaging system (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 4119-4126 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design, construction and operation of a tomographic imaging system on the Compact Toroid Injection Experiment is described. The system measures the total radiated power over energies from visible light up into the extreme ultraviolet. It then reconstructs two dimensional profiles from the data. The reconstruction routine is based on a method known as second order regularization which finds a compromise between smoothness and fit to the data. This method was found to have the best overall fidelity to test images. The hardware and overall reconstruction were calibrated using two different sources. First results from the system under real experimental conditions are presented. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1318920
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  • 19
    Electronic Resource
    Electronic Resource
    Obtaining absolute spatial flux measurements with a time-resolved pinhole camera (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 2012-2015 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A technique is described to determine the spatial x-ray flux emitted from a hohlraum wall and subsequently transmitted through a diagnostic hole. This technique uses x-ray diodes, bolometers, and a time-resolved pinhole camera to determine the spatial flux of x rays emitted through a hohlraum's diagnostic hole. The primary motivation for this analysis was the relatively long duration, nearly 100 ns, of the x-ray drive present in z-pinch driven hohlraums. This radiation causes plasma to ablate from the hohlraum walls surrounding the diagnostic hole and results in a partial obscuration that reduces the effective area over which diagnostics view the radiation. The effective change in area leads to an underestimation of the wall temperature when nonimaging diagnostics such as x-ray diodes and bolometers are used to determine power and later to infer a wall temperature. An analysis similar to the one described below is then necessary to understand the radiation environment present in x-ray driven hohlraums when these diagnostics are used and hole closure is important. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149703
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  • 20
    Electronic Resource
    Electronic Resource
    X-ray spectral power measurements utilizing the diffraction pattern of a slit (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1624-1626 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An instrument is described which can obtain x-ray spectral power measurements utilizing the diffraction pattern produced when x rays pass through a slit. Traditionally, these types of measurements yielding low to moderate spectral resolution have been made with filtered x-ray diodes or with a transmission grating. The instrument described below has several advantages over filtered x-ray diodes in determining the spectral power profile such as an insensitivity to surface contamination. In addition, this instrument does not require the use of filters which can be destroyed during a shot making absolute measurements difficult and very time consuming. The advantages over a transmission grating system include cost, mechanical robustness, and fewer components which require spectral calibration. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149642
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