We study the second harmonic generation (SHG) in a suspension of small spherical particles confined within a slab, assuming undepleted pump and applying (i) single scattering approximation and (ii) diffusion approximation. In the case (i), the angular diagram, the differential and total crossections of the SHG process, as well as the average cosine of SH scattering angle are calculated. In the case (ii), the average SH intensity is found to show no explicit dependence on the linear scattering properties of the suspension. The average intensity of SH wave scales as I 0 L/Λ 2 in both cases (i) and (ii), where I 0 is the intensity of the incident wave, L is the slab thickness, and Λ 2 is an intensity-dependent "SH scattering" length.1

We examine possible mechanisms for graphitization at dislocation cores in diamond, both as an explanation for brown coloration in natural brown diamond and as a model for annealing in amorphous carbon materials. We find a metastable structure for the 90 • partial dislocation core where bonds are broken in both single-and double-period structures leading to a row of paired sp 2 C atoms. We examine the effect of hydrogen and other impurities on this core structure both through direct interaction and potential charging effects. We also investigate a mechanism for progressive aromatization through the migration and aggregation of 30 • partial dislocations.

No abstract

No abstract

No abstract