Some Observations Concerning Electronic Densities, Electrostatic Potentials and Chemical Potentials

The hypothesis that the electronic density distribution in a molecule is qualitatively similar to the nuclear potential is shown. to be in error in at least two cases-oxirane and cubane-although it does hold true in a\u27 number of other systems. Its emphasis upon the dominant role played by electrostatic internctions with the nuclei is consistent with some approximate molecular energy formulas. However, taking the nuclear potential as an approximation to the electronic density misses the small effects that correspond to the formation of chemical bonds. It is suggested that the electronic density difference function should provide a rough picture of the local variations in the chemical potential that occur as atoms combine to form a molecule. Finally, the common practice of representing the energy and electronegativity of an interacting atom as functions only of the number of electrons associated with the atom is shown to be ina\u27dequate; some account should be taken of the changing internuclear separations

Plasma Dynamics

Contains reports on two research projects.National Science Foundation (Grant GK-37979X1)U. S. Atomic Energy Commission (Contract AT(11-1)-3070

Heavy Quarkonium and nonperturbative corrections

We analyse the possible existence of non-perturbative contributions in heavy $\bar Q Q$ systems ($\bar Q$ and $Q$ need not have the same flavour) which cannot be expressed in terms of local condensates. Starting from QCD, with well defined approximations and splitting properly the fields into large and small momentum components, we derive an effective lagrangian where hard gluons (in the non-relativistic aproximation) have been integrated out. The large momentum contributions (which are dominant) are calculated using Coulomb type states. Besides the usual condensate corrections, we see the possibility of new non-perturbative contributions. We parametrize them in terms of two low momentum correlators with Coulomb bound state energy insertions $E_n$. We realize that the Heavy Quark Effective lagrangian can be used in these correlators. We calculate the corrections that they give rise to in the decay constant, the bound state energy and the matrix elements of bilinear currents at zero recoil. We study the cut-off dependence of the new contributions and we see that it matches perfectly with that of the large momentum contributions. We consider two situations in detail: i) $E_n>> \Lambda_{QCD}$ ($M_Q \rightarrow \infty$) and ii) $E_n << \Lambda_{QCD}$, and briefly discuss the expected size of the new contributions in $\Upsilon$ , $J/\Psi$ and $B_{c}^{\ast}$ systems.Comment: 28 pages, LaTeX. Minor changes, some comments and numerical results added. To be published in Phys. Rev.

Plasma Dynamics

Contains reports on two research projects.U. S. Energy Research and Development Administration (Contract E(l1-1)-3070)National Science Foundation (Grant ENG75-06242

Plasma Dynamics

Contains research objectives and summary of research.U.S. Atomic Energy Commission (Contract AT(11-1)-3070)National Science Foundation (Grant GK-37979X)National Science Foundation (Grant GK-28282X1

Plasmas and Controlled Nuclear Fusion

Contains reports on four research project.U. S. Atomic Energy Commission (Contract AT(11-1)-3070

Plasmas and Controlled Nuclear Fusion

Contains research objectives, summary of research and reports on six research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070

Photonic band gaps and defect states induced by excitations of Bose-Einstein condensates in optical lattices

We study the interaction of a Bose-Einstein condensate, which is confined in an optical lattice, with a largely detuned light field propagating through the condensate. If the condensate is in its ground state it acts as a periodic dielectric and gives rise to photonic band gaps at optical frequencies. The band structure of the combined system of condensed lattice-atoms and photons is studied by using the concept of polaritons. If elementary excitations of the condensate are present, they will produce defect states inside the photonic band gaps. The frequency of localized defect states is calculated using the Koster-Slater model.Comment: 10 pages, 1 figure, RevTe

Plasmas and Controlled Nuclear Fusion

Contains research objectives and reports on four research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980