Crystal and molecular structures of three germylated steroids

Germylated steroids were studied by X-ray diffraction analysis for the first time. The conformational parameters of the molecules in the crystals are discussed. The three-center hypervalent O−Ge−Cl bonds are observed in two β-isomers. The geometric parameters of the hypervalent units are compared. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 116–122, January, 1999.     

STM and STS Studies of One-Dimensional Row Growth: Ag on Si(5 5 12)

We have studied the growth of Ag on Si(5 5 12) using scanning tunneling microscopy and spectroscopy (STM/STS). At metal coverages as low as 0.05 monolayer (ML), Ag forms well-ordered overlayer rows, or one-dimensional clusters, on the underlying silicon surface. To produce these ordered structures, it is necessary to anneal the surface to 450°C. As the coverage is increased above 0.05 ML, the rows grow in length and number until the surface forms a periodic array of such structures at 0.25 ML. A statistical analysis of the rows reveals a linear increase in median row length as a function of coverage. With regard to their electronic behavior, STS measurements show a significantly narrower band gap along the Ag rows than is found on the underlying silicon structures. Therefore, the deposited Ag atoms do retain some metallic behavior.     

CW and Pulsed EPR Study of Silver Nanoparticles in a SiO2 Matrix

Metallic silver nanoparticles were prepared by the sol-gel method in an SiO2 matrix. The process includes complexation of silicon alkoxides with metal salts, hydrolysis, polycondensation, formation of powder, and subsequent thermal treatment first in oxidizing and second in reducing atmospheres. The sizes of metallic particles were determined both by X-ray diffraction and transmission electron microscopy. These measurements revealed sizes of metallic particles between 1 and 20 nm, depending upon processing conditions. The magnetic properties were investigated using electron paramagnetic resonance spectroscopy in the temperature range between 4 and 300 K. The spin-lattice relaxation time T1 was measured by pulsed EPR. The temperature dependence of T1 is described by the relation 1/T1 Tn, where 0.4 < n < 1. This behavior is unusual and different from any well-known relaxation processes such as Raman, Direct or the Orbach-Aminov.