Vibrational relaxation in the group IVA trimethylmetal chlorides

The temperature dependence of the polarized and depolarized Raman spectra of the ν₂, ν₄, ν₆ and ν₇ modes were measured for t-butyl chloride and the analogous group IVA trimethylmetal chrlorides (silicon, germanium and tin). Analysis of the lineshapes revealed that isotropic second moments and vibrational relaxation times for a given mode remained approximately constant through the series. This tranferability of relaxation parameters between molecules extended to modulation times calculated from the Kubo formalism. The above results are in contrast to earlier studies on molecules of dissimilar structure. They provide some preliminary evidence that the mechanism of vibrational relaxation may be the same for equivalent modes in members of the series.     

A filtration problem in a porous medium with variable permeability

Sunto Un problema di frontiera libera (moto di un fluido attraverso una diga in terra non omogenea) è ricondotto allo studio di una disequazione variazionale. Si danno condizioni sul coefficiente di permeabilità sufficienti ad assicurare che la parte bagnata della diga è un sottografico.

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Entrata in Redazione il 30 giugno 1976.

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This paper is partially supported by National Science Foundation Grant MPS 72-04959 A02, and by C.N.R. of Italy through L.A.N. of Pavia.     

The study of solute—solute forces by NMR relaxation

By calculation it is found that the enhancement of the NMR relaxation rate of ⁷Li⁺ by Mn²⁺ or Ni²⁺ in aqueous solution is measurably different for two models which are consistent with other magnetic relaxation and thermodynamic data for the solutions.     

The coordination geometry of water in some salt hydrates

The orientations of water molecules next to metal ions in salt hydrates are useful indications of the orientations which may be expected for water molecules which are next to metal ions in aqueous solution. A survey of the data for the salt hydrates shows that a water molecule may often be tetrahedral (i.e., coordinated to the metal ion, accepting a hydrogen bond from another water molecule, and donating two hydrogen bonds) if it is next to a +1 ion, a+2 ion, or a+3 ion of the rare earth series, although apparently not for smaller +3 ions.     

The maximum entropy determination of nuclear densities of calcium isotopes from elastic scattering of alpha particles

Radial moments of the real part of the optical potential for elastic scattering of 104 MeV α particles are used as constraints, in determining the nuclear density of maximal entropy. The potential is related to the density by the folding model.     

The influence of an electric field on a hydrogen atom confined to boxes of different shapes

The ground state energy of a hydrogen atom confined to a box, in the presence of an electric field is calculated. Boxes of various shapes are applied in order to demonstrate the shape's influence on that energy level. The procedure consists of numerically solving the two-dimensional Schrödinger equation using a finite element package.