6405the function vRAB is small. The expansions of the two Bessel functions are KO(YRAB) = -In (vRAB)ym + In (2) ... K~(YRAB) = (vRAB)-' ...where ym is the Euler Mascharoni constant. Using these two expressions in eq 13, we obtain for the diffusion coefficientUsing the Arrhenius expression for the diffusion coefficient and for the diffusion-controlled rate coefficient and the definition of Y , given in eq 12, we arrive at kdc 217 Using the definition of T given in eq 2, we expand the rightmost expression in eq 22We now defineUsing these two definitions and taking the logarithm of both sides of eq 23, we arrive atFinally under the assumption that the prefactors Do and ko are similarly temperature dependent and differentiating eq 25 results in Registry No. Ru(bpy)32+, 15158-62-0; 02, 7782-44-7; silica, 7631-86-9. References and Notes(1) Photochemistry on Solid Surfaces; Anpo, M., Matsuura, T., Eds.; Elsevier, Amsterdam, 1989. Photochemistry in Constrained and Organized Media; Ramamurthy, V., Ed.; VCH: New York, 1991.(2) Rideal, E. K.

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1997 magnetic resonance, nuclear quadrupole resonance magnetic resonance, nuclear quadrupole resonance (solids and liquids) D 6560 -015A 31P Spin Diffusion and 31P-113Cd CP/MAS NMR Study of Polycrystalline Cd3(PO4)2.-Quantitative analysis of the 31P spin diffusion experiments as a function of mixing times yields an unambiguous assignment of the six 31P resonances to the six independent crystallographic P sites in the known structure of Cd3(PO4)2. The internuclear P-P connectivities determined by NMR are in agreement with the single crystal XRD P-P distances. In addition, the unambiguous assignment of all 113Cd resonances to the nine crystallographically independent Cd sites is achieved. -(DUSOLD, S.; KUEMMERLEN, J.; SCHALLER, T.; SEBALD, A.; DOLLASE, W. A.; J.

1997 magnetic resonance, nuclear quadrupole resonance magnetic resonance, nuclear quadrupole resonance (solids and liquids) D 6560 -008A 31P NMR Study of Solid Compounds MxP2O7.-The title studies are performed for Na4P2O7·10H2O representing a model compound containing an isolated P2O4-7 31P spin pair and for Cd2P2O7 containing spatially nonisolated P2O4-7 units. The properties of their 31P spin systems are compared under conditions of straightforward 1D 31P MAS, of 31P spin echo, and rf-driven spin diffusion experiments on nonspinning samples. For Cd2P2O7 the magnitude of 2J(31PA 31PB) is determined experimentally.-(DU-SOLD, S.; KUEMMERLEN, J.; SEBALD, A.; J.