Index of content:
Volume 110, Issue 22, 08 June 1999
110(1999); http://dx.doi.org/10.1063/1.479007View Description Hide Description
During experiments to detect carbon chain molecules in the laboratory, an electrical discharge through a dilute mixture of silane and diacetylene was found to produce a molecule of unusual structure that is composed of only silicon and carbon. On spectroscopicanalysis this molecule has been shown to have the elemental formula a closed-shell singlet electronic ground state, and a planar rhomboidal geometry that consists of atoms in the shape of a distorted four-membered ring with a transannular carbon–carbon bond. Rhomboidal is isovalent with rhombic a long predicted low-lying isomer of of similar structure which has so far eluded spectroscopic detection. Strong lines of can be observed under a wide range of experimental conditions, suggesting that this molecule is quite stable, and that kinetic and thermodynamic factors favor its formation. Radio emission lines of have now been detected in space in the molecular envelope of the carbon-rich star IRC+10216.
110(1999); http://dx.doi.org/10.1063/1.479008View Description Hide Description
The vibrational OH stretch spectra have been measured for the size-selected pure water clusters In contrast to =8–10 clusters, which exhibit three distinct bands corresponding to three distinct types of OH bonds, the heptamer spectrum displays seven bands spanning the range from 2935 to 3720 cm−1. Calculations suggest that the spectra originate from two isomers, derived from the octamer cube by removal of either one double donor or one double acceptor water molecule.
Toward a global and causal understanding of the unusual Rydberg state potential energy curves of the heteronuclear rare gas dimers110(1999); http://dx.doi.org/10.1063/1.479009View Description Hide Description
Primitive calculations, based on simple physical concepts, have been found to explain the unusual excited state potential energy curves deduced from RgXe (Rg=Kr, Ar, Ne), two-photon spectra. The irregularities in the potentials and their dependence on the effective principle quantum number, are attributed to repulsive exchange interactions between electrons in closed shell orbitals of the ground state Rg atom and the Rydberg electron. The internuclear distance dependence of these exchange interactions reflect the nodal structure of the radial probability distribution of the Rydberg orbital.
Living polymerization of -methylstyrene in tetrahydrofuran followed by dynamic light scattering near its polymerization temperature110(1999); http://dx.doi.org/10.1063/1.479010View Description Hide Description
We followed the polymerization reaction of living poly--methylstyrene in a solution of tetrahydrofuran as a function of temperature, near its ceiling temperature, using dynamic light scattering. We obtained three different relaxation times revealing three kinds of macromolecular species in the solution. One of the relaxation times corresponded to the formation of living polymer chains. In this particular case, we found that the average relaxation time increased as temperature was lowered due to polymer growth. Nevertheless, it did not follow the same track along a cooling–heating cycle. These results are consistent with an incomplete depolymerization reaction. For the other two species, we propose that they were the result of ionic aggregation.
110(1999); http://dx.doi.org/10.1063/1.479011View Description Hide Description
We present a new experimental approach to the study of vibrational relaxation of highly vibrationally excited molecules at solid surfaces. We observe NO in and 15 losing up to five vibrational quanta in collisions with an O-covered coppersurface. The data indicate this vibrational relaxation occurs via a direct scattering mechanism.