Magnetic relaxation in one-dimensional exchange-coupled (CH^NMnC^ is found to be dramatically different than it is in three-dimensional exchange-narrowed paramagnets. A theory which accounts properly for the special long-time persistence of spin-correlation functions in one dimension is shown to explain the observed behavior.

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We report the first observation of sum frequency generation (SFG) photons on high-surface-area powders, critically important materials in heterogeneous catalysis. We utilize SFG in total internal reflection (TIR) geometry and show that the TIR-SFG approach markedly reduces the destructive interference associated with nonlinear optical spectroscopy of small particle surfaces, making SFG studies of high-surface-area powders possible. The index of refraction of materials and their distance from the TIR-SFG prism are key parameters in generating and detecting the sum frequency signal. We find that TIR-SFG is highly sensitive to capillary condensation. To demonstrate the capability of the TIR-SFG technique, we measure the thermodynamics of methanol adsorption and desorption on high-surface-area SiO2.

case of indirect excitons 9 this interaction is not forbidden by translational symmetry. It may be realized in the form of simultaneous scattering of electrons and holes between different X points by either Coulomb or electron-phonon interaction.A quantitative determination of the matrix elements in question and the deformation potentials is difficult because of uncertainties in the decomposition of overlapping bands A, B, and C. At the present time we can only give a rough estimate of these quantities. Using the hydrostatic deformation potential 10 to eliminate A x we find that A 3 »7 eV per unit shear deformation \e ee -?(e xx + e yy ). This rather large value again indicates that the exciton transition does not take place at the center of the Brillouin zone but that a star degeneracy is involved. Preliminary analysis shows that E X

The Knight shift and electric quadrupole coupling constant have been measured as a function of lithium concentration in the continuous intercalation phase LixTiS2 where 0⩽x⩽1. These NMR data, when compared with observations of c axis dilation and thermodynamics of this phase, suggest the donation of an appreciable fraction of the Li 2s electron to the TiS2 layers during intercalation, with the fraction diminishing as x increases. The relation of the charge donated to each of the observed quantities is discussed.