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  • American Institute of Physics (AIP)  (55)
  • American Chemical Society (ACS)
  • 1995-1999  (55)
  • 1
    Electronic Resource
    Electronic Resource
    Moyal–Nahm equations (1999)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 40 (1999), S. 2539-2548 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Various aspects of the Nahm equations in three and seven dimensions are investigated. The residues of the variables at simple poles in the seven-dimensional case form an algebra. A large class of matrix representations of this algebra is constructed. The large N limit of these equations is taken by replacing the commutators by Moyal brackets, and a set of nontrivial solutions in a generalized form of Wigner distribution functions is obtained. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.532713
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Polarization around an ion in a dielectric continuum with truncated electrostatic interactions (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 10679-10692 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In order to reduce computational effort and to allow for the use of periodic boundary conditions, electrostatic interactions in explicit solvent simulations of molecular systems do not obey Coulomb's law. Instead, a number of "effective potentials" have been proposed, including truncated Coulomb, shifted, switched, reaction-field corrected, or Ewald potentials. The present study compares the performance of these schemes in the context of ionic solvation. To this purpose, a generalized form of the Born continuum model for ion solvation is developed, where ion–solvent and solvent–solvent interactions are determined by these effective potentials instead of Coulomb's law. An integral equation is formulated for calculating the polarization around a spherical ion from which the solvation free energy can be extracted. Comparison of the polarizations and free energies calculated for specific effective potentials and the exact Born result permits an assessment of the accuracy of these different schemes. Additionally, the present formalism can be used to develop corrections to the ionic solvation free energies calculated by molecular simulations implementing such effective potentials. Finally, an arbitrary effective potential is optimized to reproduce the Born polarization. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479013
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  • 10
    Electronic Resource
    Electronic Resource
    A (1+1′)+1 multiphoton ionization study of CS2 in the 68 500–73 000 cm−1 energy region. The 3d and 5s Rydberg states (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 62-67 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The two color (1+1′)+1 resonance enhanced multiphoton ionization spectrum of CS2 has been recorded in the 68 500–73 000 cm−1 excitation energy range. Strong bands were recorded in the 68 800–70 000 cm−1 region and the upper states assigned to 3d and 5s gerade Rydberg states with quantum defects of 0.0 and 2.0, respectively. The two color spectra were recorded in both parallel and crossed polarization configurations to assist in state symmetry assignments. Some weaker features in the 70 500–71 500 cm−1 region are most likely associated with vibronically induced transitions to a 5p Rydberg state. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471881
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