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  • 1
    Electronic Resource
    Electronic Resource
    Reverse saturable absorption in C60-doped porous glasses studied by single- and double-pulse pump–probe experiments (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5929-5937 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the nonlinear absorption of C60-doped porous sol-gel glasses by single- and double-pulse pump–probe experiments. We find that the reverse saturable absorption (RSA) of these samples can be explained in the frame of a five level system as it is commonly used for C60 solutions. We observe a strong saturation of the RSA at high fluences, especially if the molecules are prepared in the triplet state. In a double-pulse pump–probe experiment we measure the triplet quantum yield for C60 solutions (0.8) and doped glasses (0.25) and the singlet and triplet absorption cross sections. In the first excited singlet state (S1) lifetimes of 1 ns and 65 ps are determined in solutions and glasses, respectively. We find that the dynamics of both depopulation processes, direct S1–S0 relaxation, and intersystem crossing is faster in glasses than in the case where C60 is in solution in a liquid aromatic solvent. We tentatively explain these findings by the absence of a stabilizing solvent and a perturbation of the molecular energy levels due to interaction with the solid glass matrix. We finally determine the lifetime of the triplet states in our glass samples to 2 μs. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479888
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  • 2
    Electronic Resource
    Electronic Resource
    Optical limiting properties and dynamics of induced absorption in C60-doped solid xerogel matrices (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 8599-8604 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present measurements of induced absorption and its dynamics in C60-doped solid xerogel matrices. The measurements are performed in a pump-test geometry using picosecond pulses generated from a frequency doubled mode locked Nd:YAG laser at 532 nm. We observe an induced absorption leading to optical limiting. We find outstanding optical limiting qualities for single shot excitation but some degradation above a certain threshold intensity for repetitive pulses. Below this degradation threshold, the material is stable and its limiting dynamics is studied. A decrease of the initial laser-induced absorption with a time constant of 150 ps is observed, down to a very long-lived constant level. We attribute this dynamics of induced absorption to a transition from excited singlet to triplet electronic states in the C60 molecule. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476290
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  • 3
    Electronic Resource
    Electronic Resource
    Excitons in quantum well wires: V-shaped wire, T-shaped wire and strain-induced lateral confinement (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1389-1393 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We calculated the energy and the wave function of the exciton for i) a V-shaped quantum wire, ii) a T-shaped quantum wire and iii) a quantum wire resulting from strain-induced lateral confinement. The full Luttinger and Bir-Pikus Hamiltonian are taken into account in the three calculations. We used different parameters inside the well and at the barrier. The basis states |3/2m〉 are defined with respect to [110], the direction of the wire in the three kinds of structures, instead of the usual [001] direction. The hole dispersion curve allows one to define an effective mass which is to be introduced in the variational calculation of the exciton binding energy. We show that the hole is confined in a wire only in case i).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457215
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetische Kernresonanz und Festkörperphysik (1970)
    Springer
    Cellular and molecular life sciences 26 (1970), S. 1-7 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nuclear magnetic resonance (NMR) deals with isotopes possessing a nuclear magnetic dipole moment. The nuclei are used as probes to explore the internal magnetic fields in solids. Thus NMR has become a new tool in solid-state physics. Some typical examples of the application of NMR to solid-state problems are discussed. The location and orientation of water molecules in crystals are determined by NMR with relative ease. The second moment of an NMR line shape yields information on the structure as well as on the mobility of the atoms. The various types of resonance frequency shifts may be used for the understanding of the interactions and bonds in the solid and the dynamics of the crystal lattice. Very important are nuclei possessing both a magnetic dipole and an electric quadrupole moment. They serve as very sensitive detectors of the internal electric fields prevailing in solids. Apart from further structural information, NMR spectra influenced by electric quadrupole interaction may be used for studying such topics as aluminium-silicon ordering in feldspars or phase transitions in ferroelectrics. The utility of NMR in treating problems of the bonding is exemplified by showing that the covalent effects in the alkali halides are very small. Some investigations of ferromagnetism, antiferromagnetism and superconductivity are mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01900352
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  • 5
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance of 7Li and 23Na in zektzerite, NaLiZrSi6O15 (1989)
    Springer
    Physics and chemistry of minerals 16 (1989), S. 720-724 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The electric field gradient (EFG) tensors of 7Li and 23Na in a zektzerite, NaLiZrSi6O15 single crystal have been determined by the nuclear magnetic resonance technique. The quadrupole coupling constants, e2qQ/h and the asymmetry parameters, η, for 7Li are 119 ± 5 kHz, 0.05 and for 23Na 2.42 ± 0.15 MHz, 0.86 respectively. In both cases, the EFG tensors show the two-fold site-symmetries at the Li- and Na-sites. For 7Li, the magnitude of the quadrupole coupling constant and the principal axis of the EFG tensor reflect the large angular distortion of the [LiO4] tetrahedron. The large quadrupole coupling constant of 23Na indicates a high degree of distortion of the Na coordination polyhedron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223323
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  • 6
    Electronic Resource
    Electronic Resource
    Two-pion Bose-Einstein correlations in nuclear collisions at 200 GeV per nucleon (1995)
    Springer
    The European physical journal 66 (1995), S. 77-88 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of a pion interferometry analysis are presented for the reactions S+C, S+S, S+Cu, S+Ag, S+Au and O+Au at 200 GeV per nucleon. Correlation functions were measured for pairs of negative pions in narrow windows of transverse momentum and rapidity, as a function of the three components of the momentum difference vector in cylindrical coordinates. The measured two-pion correlation functions suggest a space-time evolution of the system which proceeds in the following way for central nucleus-nucleus collisions. After interpenetration of the incident nuclei, the pion source expands in a boost invariant way along the collision axis. Estimates for the proper time interval between the onset of expansion and pion decoupling, as well as for the duration of pion emission are ∼ 4 fm/c and 〈2 fm/c, respectively. Thek T dependence observed forR S is consistent with the effect of resonance decays, alone or combined with slow transverse expansion. A linear dependence of the decoupling volume on the multiplicity is observed and indicates pion decoupling at a constant particle density. Presently available model predictions are briefly discussed
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01496582
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  • 7
    Electronic Resource
    Electronic Resource
    Interaction-assisted propagation of Coulomb-correlated electron-hole pairs in disordered semiconductors (1999)
    Springer
    The European physical journal 10 (1999), S. 145-148 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 73.20.Dx Electron states in low-dimensional structures (superlattices, quantum well structures and multilayers) - 72.15.Rn Localization effects (Anderson or weak localization) - 78.66.-w Optical properties of specific thin films, surfaces, and low-dimensional structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A two-band model of a disordered semiconductor is used to analyze dynamical interaction induced weakening of localization in a system that is accessible to experimental verification. The results show a dependence on the sign of the two-particle interaction and on the optical excitation energy of the Coulomb-correlated electron-hole pair.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050837
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