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  • American Chemical Society  (278)
  • American Institute of Physics (AIP)  (55)
  • American Association of Petroleum Geologists (AAPG)
  • 1995-1999  (277)
  • 1930-1934  (56)
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  • 21
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2295-2301 
    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
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  • 22
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2063-2079 
    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.
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  • 23
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3956-3961 
    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.
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  • 24
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3968-3976 
    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.
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  • 25
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 11100-11107 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using redundant inverse-power distance coordinates we present a series of optimizations on randomly generated argon clusters containing 12, 24, and 48 argon atoms. Our results clearly show that inverse distance coordinates perform significantly better for optimizing the geometries of atomic clusters than either Cartesian or natural/delocalized internal coordinates. The potential utility of these coordinates for global optimization is discussed. © 1996 American Institute of Physics.
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  • 26
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6147-6153 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The polarization dependence of the (2+1) and (3+1) resonance enhanced multiphoton ionization of OCS have been investigated in the 70 500–74 500 cm−1 energy region. This region contains a complex system of bands arising from the excitation of the 4p Rydberg states. The symmetry of most of the observed bands have been unambiguously determined based on the intensity changes of the two and three photon resonant spectra using both linearly and circularly polarized light. These results generally confirm the assignments suggested in a previous study. New bands have also been observed and some new assignments are proposed. The vibrational frequencies ν1, ν2, and ν3 of the Rydberg states in that energy region are determined. © 1996 American Institute of Physics.
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  • 27
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 62-67 
    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.
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  • 28
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 3862-3866 
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 29
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of natural products 58 (1995), S. 1596-1599 
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 30
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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