Weak Interaction Energies Research Articles

Summary of in situ epitaxial nucleation and growth measurements

Semiconducting single-crystal thin films of PbSe and chemically prethinned samples of bulk Si were found to be suitable substrate materials for in situ TEM studies of autoepitaxial and heteroepitaxial film nucleation and growth processes. In situ surface cleaning by either evaporation or sputtering was used in conjunction with a UHV background environment to ensure reliable results. The epitaxial systems which have been studied most extensively are Au and Ag on (100)-oriented PbSe. Detailed results obtained include (a) identification of structure (polymorphism), crystalline perfection, and stoichiometry of the initial and the autoepitaxially thickened PbSe substrates; (b) quantitative nucleation and growth kinetic measurements at low supersaturation of Ag on PbSe—a system characterized by weak interaction energies and high surface mobilities; (c) observations of epitaxial orientations and the development of epitaxy during the deposition process; and (d) demonstration of strong substrate/overgrowth reactions involving alloying and interdiffusion.

Paramagnetic Susceptibilities of Some DPPH Derivatives

Abstract The static magnetic susceptibilities of poly crystalline samples of 1,1-bis(p-chlorophenyl)-2-picrylhydrazyl (Cl-DPPH), 1,1-bis(p-bromophenyl)-2-picrylhydrazyl (Br-DPPH), and 1,1-bis (p-methoxyphenyl)-2-picrylhydrazyl (CH3O-DPPH) were measured in the temperature range from 10°K to 300°K. These three substances showed strong paramagnetism comparable to that of DPPH, having relatively weak interaction energies between their unpaired electrons. Of these, the paramagnetic susceptibility of CH3O-DPPH was analysed on the basis of the singlet-triplet model with the energy separation of 2J/k=33.8°K.

Magnetic and Electrical Properties of Small Diatomic Molecules. I. Diamagnetic Susceptibility, Proton-Shielding Constant, and Electric Polarizability of the Hydrogen Molecule

An unambiguous exact variational procedure is given for the calculation of certain weak interaction energies starting from any given approximate ground-state wavefunction. The method is illustrated by numerous calculations on the hydrogen molecule using five different ground-state wavefunctions.