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  • 1
    Electronic Resource
    Electronic Resource
    Solvation state selective excitation in resonance Raman spectroscopy. I. Experimental study on the C(Double Bond)N and the C(Double Bond)O stretching modes of phenol blue (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9075-9083 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the excitation photon energy dependence of the resonance Raman spectra of a solvatochromic dye, phenol blue (PB) in various solvents from nonpolar to dipolar ones, including supercritical fluids of trifluoromethane and carbon dioxide. We have found that the band peak positions of the C(Double Bond)N stretching mode of PB appear to change with the excitation laser frequency in polar solvents. On the other hand, no dependence of the band peak positions on the excitation frequency is found in nonpolar solvents. The peak positions of the C(Double Bond)O stretching mode also show small excitation energy dependence in chloroform and in methanol. The extent of the excitation energy dependence is correlated with the amount of the fluctuation of the local field on PB molecule exerted by the solvent, which had been estimated from the bandwidths of the absorption and the Raman spectra of PB in solution. The IR absorption spectra of PB are measured in chloroform and carbon tetrachloride, and compared with the Raman spectra in the same solvents. The excitation energy dependence is explained by the solvation state selective excitation in the resonance Raman spectroscopy, that is, the inhomogeneity that appears in the absorption spectra of PB also appears in the resonance Raman process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477463
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  • 2
    Electronic Resource
    Electronic Resource
    Electron spin resonance studies in β-FeSi2 crystals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1678-1681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron spin resonance studies have been carried out in the temperature range 130–300 K on semiconducting β-FeSi2 single crystals grown by a chemical vapor transport technique. Two anisotropic doublets with apparent g factors in the range 2.025–2.05 and 1.98–2.03, as well as one complex signal having an isotropic g factor of 2.0195 and exhibiting a five-line hyperfine structure, have been detected. The doublet signals are believed to arise from spin triplet (S=1) states of, presumably, substitutional Ni2+ transition ions, whereas the signal exhibiting the hyperfine structure has been attributed to the spin of a hole, captured by silicon vacancy and interacting with nuclear spins of four iron atoms in the first shell surrounding of the silicon vacancy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362967
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of the solvent density and species on the back-electron transfer rate in the hexamethylbenzene/tetracyanoethylene charge-transfer complex (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1485-1498 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The back-electron transfer (b-ET) process in the hexamethylbenzene/tetracyanoethylene charge-transfer complex was studied by the transient absorption spectroscopy in several fluids (ethane, nitrous oxide, carbon dioxide, and trifluoromethane) from the critical density to twice that of it at 323.2 K. The b-ET rate was determined by the decay rate of the excited state absorption. The b-ET rate increased with the increase of solvent density in carbon dioxide and nitrous oxide. The b-ET rate also increased in the order of ethane, nitrous oxide, carbon dioxide, and trifluoromethane, compared at the similar reduced density divided by the solvent critical density. Based on the formulation by Marcus and Jortner, the reaction free energy and the solvent reorganization energy were estimated from the change of the absorption spectrum relative to the gaseous phase spectrum, simply by assuming that the intramolecular reorganization energy does not depend on the solvent density and the species. The reaction free energy and the solvent reorganization energy in fluids obtained in this way were almost linearly correlated, and the density dependence was larger in the lower density region. The b-ET rates in various conditions showed a good correlation with the reaction free energy estimated from the spectral simulation. The b-ET rate showed a significant isotope effect by perdeuteriation of hexamethylbenzene as is predicted by the fluorescence quantum yield [K. Kulinowski et al., J. Phys. Chem. 99, 17715 (1995)], which could not be reproduced by this model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475520
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  • 4
    Electronic Resource
    Electronic Resource
    The excitation energy dependence of the Raman–Stokes shift: The resonance Raman spectra of phenol blue in methanol (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 4436-4438 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We found that the Raman–Stokes shift of the C(Double Bond)N stretching mode of Phenol Blue changes with excitation energy; the frequency of this Raman band increased with an increase of the excitation energy, whereas the bandwidth was almost the same. The origin of the excitation energy dependence is discussed in connection with the correlation of the effect of the solvent fluctuation on the electronic transition energy and the vibrational frequency. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474785
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  • 5
    Electronic Resource
    Electronic Resource
    The role of the attractive and the repulsive interactions in the nonpolar solvation dynamics in simple fluids from the gas-like to the liquid-like densities (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 4169-4185 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have performed molecular dynamics (MD) simulations of the nonpolar solvation dynamics in simple fluids composed of particles interacting through the Lennard-Jones (LJ) 12–6 potential or its repulsive part. The attractive or the repulsive part of the solute–solvent interaction is assumed to change on the excitation of a solute. We have followed the transition energy fluctuation of the solute by the equilibrium simulation. The division of the LJ potential followed the method of WCA [J. W. Weeks, D. Chandler, and H. C. Andersen, J. Chem. Phys. 54, 5237 (1971)]. We have surveyed over a wide solvent density region from gas-like to liquid-like densities at the constant temperature. When the attractive part changes, the relaxation becomes faster with an increase of the solvent density. This result contradicts with previous theories that treat the nonpolar solvation dynamics in terms of the diffusion of solvent particles. The time scale of the initial part of the relaxation is well correlated with the static fluctuation divided by the static average, which suggests the importance of the curvature of the free energy surface in the initial part of the solvation. When the repulsive part changes, the initial part of the relaxation is almost density independent, determined by the binary motion between solute and solvent. It is consistent with the result that the static fluctuation is almost proportional to the static average, which indicates the absence of the static correlation between solvent particles. On the other hand, the solvation correlation function shows rather complicated density dependence at the longer time scale. In the case of the binary mixture solvent, the relaxation time is inversely proportional to the diffusion coefficient. On the basis of the nonpolar solvation dynamics, the validity of the isolated binary collision model for the vibrational energy relaxation is also discussed, and the recent hydrodynamic theory on the vibrational energy relaxation [B. J. Cherayil and M. D. Feyer, J. Chem. Phys. 107, 7642 (1997)] is critically examined. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479715
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of solvent density and species on static and dynamic fluorescence Stokes shifts of coumarin 153 (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5474-5484 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Solvent density dependence of the absorption and fluorescence spectra of coumarin 153 in argon (Ar), ethane (C2H6), carbon dioxide (CO2), and trifluoromethane (CF3H) has been studied at 323.2 K over a wide density region up to ρr∼3, where ρr is the reduced density by the critical density (ρc) of the solvent (ρr≡ρ/ρc). By analyzing the line shape functions of the absorption and fluorescence spectra, the first moment and the full width of the half maximum (FWHM) have been determined. Both the free energy difference (ΔG) between the ground and the S1 states and the fluorescence Stokes shift (Δν), evaluated by the first moments of the absorption and fluorescence line shape functions, show larger shift to the values in vapor in the order of Ar, C2H6, CO2, and CF3H if compared at the same ρr. There are three characteristic density regions on the density dependence of ΔG and Δν; these values show larger dependence in the lower-density region (ρr〈0.5) and the higher-density region (ρr〉2), than that in the medium-density region. The solvent density and species dependence of the FWHM of the absorption spectrum is quite similar to that of Δν. The density dependence of Δν and FWHM in Ar and C2H6 indicates that the intramolecular reorganization energy decreases with increasing the solvent density, while the effect is small. We have estimated the solvent reorganization energy (λS) in CO2 and CF3H by assuming no contribution of λS in C2H6 and Ar. We have demonstrated that the dielectric continuum model makes a good prediction on the relation between ΔG and λS, while it is poor on their density dependence. The invariance of ΔG and λS in the medium-density region can be interpreted as the density saturation around the solute molecule. In the lower-density region (ρr〈∼0.5), the way of the solvation is suggested to be different from those in the medium- and high-density regions. The lifetime of S1 shows a large dependence on the solvent density and species in the very low-density region (ρr∼0.05). We have also found that slow solvation dynamics exists in the lower-density region of CF3H. The origin of the dynamics is discussed in relation with the static Stokes shift. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479808
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  • 7
    Electronic Resource
    Electronic Resource
    Vibrational energy relaxation of azulene in the S2 state. II. Solvent density dependence (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 4340-4348 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the vibrational energy relaxation of azulene in the S2 state in ethane, carbon dioxide, and xenon over a wide density region by the time-resolved fluorescence spectroscopy. The reduced density of the solvent (the density divided by the critical density) has been changed from the gaslike one (lower than 0.05) to the liquidlike one (2.8 for ethane, 2.7 for carbon dioxide, and 2.0 for xenon). The density dependence of the relaxation rate is compared with that of azulene in the S0 state [D. Schwarzer, J. Troe, M. Votsmeier, and M. Zerezke, J. Chem. Phys. 105, 3121 (1996)]. Although the absolute rate largely depends on the electronic state, the density dependence of the relaxation rates is roughly the same for both electronic states, which can be considered as a side-proof of the isolated binary collision model. Possible origins for the validity of the isolated binary collision model are discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288391
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  • 8
    Electronic Resource
    Electronic Resource
    Solvation state selective excitation in resonance Raman spectroscopy. II. Theoretical calculation (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9084-9095 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have reported in the previous paper [J. Chem. Phys. 109, 9075 (1998)] that the Raman Stokes shifts of the C(Double Bond)O and the C(Double Bond)N stretching modes in the resonance Raman spectra of a solvatochromic dye, phenol blue (PB), appear to depend on the excitation photon energy in polar or protic solvents. The reason was ascribed to the solvation state selective excitation due to the inhomogeneous distribution of the solvation environment. In this paper we have made a theoretical model calculation to demonstrate that the solvation state selective excitation indeed brings about the excitation energy dependence of the resonance Raman Stokes shift in solution. In our model, both the electronic and the vibrational transitions are linearly coupled to the same harmonic bath, to embody the coupling between the fluctuations of the electronic and the vibrational transition energies. The absorption and the resonance Raman cross sections are formulated for this model on the basis of the time dependent path integral method. In the formulation, the finite relaxation time of the bath mode and the vibrational progressions in the absorption spectra are also taken into account. We have calculated the resonance Raman spectra at various excitation photon energies for the model system probable for PB in methanol. The parameters for the calculation are estimated from the analysis of the absorption and the resonance Raman spectra. It is demonstrated that the Raman Stokes shift indeed depends on the excitation energy for this model. It is noted that the vibrational dephasing due to the coupling with the solvent bath mode should be faster than the relaxation time of the bath mode for the excitation energy dependence of the Raman Stokes shift to be observed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477464
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  • 9
    Electronic Resource
    Electronic Resource
    Surface-enhanced Raman scattering of cytochromes c3 adsorbed on silver electrode and their redox behavior (1987)
    s.l. : American Chemical Society
    Langmuir 3 (1987), S. 982-986 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00078a018
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  • 10
    Electronic Resource
    Electronic Resource
    Investigation of the fabrication process of hot-worked stainless-steel and Mo sheathed PbMo6 S8 wires (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 766-771 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stainless-steel and Mo sheathed PbMo6 S8 wires have been fabricated by hot working from modified PbS, Mo, and MoS2 mixed powders which were prepared by reacting Pb, Mo, and S at 530 °C. Critical current densities were investigated for different preparation conditions, and it is revealed that obtaining continuous current path between PbMo6 S8 grains is the most important factor to achieve high critical current density. The Jc value of 2.8×104 A/cm2 (8 T), 7.8×103 A/cm2 (15 T), and 1.3×103 A/cm2 (23 T) was observed for the PbMo6 S7.0 wire heat treated at 700 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341922
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