Designing spin-1 lattice models using polar molecules

We describe how to design a large class of always on spin-1 interactions between polar molecules trapped in an optical lattice. The spin degrees of freedom correspond to the hyperfine levels of a ro-vibrational ground state molecule. Interactions are induced using a microwave field to mix ground states in one hyperfine manifold with the spin entangled dipole-dipole coupled excited states. Using multiple fields anistropic models in one, two, or three dimensions, can be built with tunable spatial range. An illustrative example in one dimension is the generalized Haldane model, which at a specific parameter has a gapped valence bond solid ground state. The interaction strengths are large compared to decoherence rates and should allow for probing the rich phase structure of strongly correlated systems, including dimerized and gapped phases.Comment: 24 pages, 5 figure

Enhancement of the electric dipole moment of the electron in BaF molecule

We report results of ab initio calculation of the spin-rotational Hamiltonian parameters including P- and P,T-odd terms for the BaF molecule. The ground state wave function of BaF molecule is found with the help of the Relativistic Effective Core Potential method followed by the restoration of molecular four-component spinors in the core region of barium in the framework of a non-variational procedure. Core polarization effects are included with the help of the atomic Many Body Perturbation Theory for Barium atom. For the hyperfine constants the accuracy of this method is about 5-10%.Comment: 8 pages, REVTEX, report at II International Symposium on Symmetries in Subatomic Physics, Seattle 199

Two-step method for precise calculation of core properties in molecules

Precise calculations of core properties in heavy-atom systems which are described by the operators heavily concentrated in atomic cores, like to hyperfine structure and P,T-parity nonconservation effects, usually require accounting for relativistic effects. Unfortunately, completely relativistic treatment of molecules containing heavy elements is very consuming already at the stages of calculation and transformation of two-electron integrals with a basis set of four-component spinors. In turn, the relativistic effective core potential (RECP) calculations of valence (spectroscopic, chemical etc.) properties of molecules are very popular because the RECP method allows one to treat quite satisfactory the correlation and relativistic effects for the valence electrons of a molecule and to reduce significantly the computational efforts. The valence molecular spinors are usually smoothed in atomic cores and, as a result, direct calculation of electronic densities near heavy nuclei is impossible. In the paper, the methods of nonvariational and variational one-center restoration of correct shapes of four-component spinors in atomic cores after a two-component RECP calculation of a molecule are discussed. Their efficiency is illustrated in correlation calculations of hyperfine structure and parity nonconservation effects in heavy-atom molecules YbF, BaF, TlF, and PbO.Comment: 20 pages, 3 tables, lecture on the Fock school-conference (Novgorod-the-Great, Russia, April 2004

Sicherheit bei Halbleiterfertigungsgeräten

Sicherheit ist ein heute recht oft verwendetes Schlagwort. Häufig versteht man darunter, je nach Standpunkt, etwas ganz anderes. Bei Halbleiterfertigungsgeräten kann man "Sicherheit" im Zusammenhang mit vier verschiedenen Aspekten gebrauchen: - Halbleiterfertigungsgeräte sollen sicher für das Bedienpersonal sein, dieses also nicht gefährden, z.B. durch Strahlung, toxische Gase oder hohe Spannungen. - Halbleiterfertigungsgeräte sollen sicher für die Umwelt sein, d.h. beispielsweise keine toxischen Gase und Chemikalien freisetzen. - Halbleiterfertigungsgeräte sollen sicher hinsichtlich des Prozeßergebnisses sein, d.h. die gewünschte Schichtdicke, Linienbreite oder Dotierungskonzentration soll reproduzierbar und homogen über die Scheibe ohne Nachregelung am Ende des Prozeßschrittes vorliegen. - Schließlich sollen Halbleiterfertigungsgeräte auch betriebssicher sein, d.h. eine möglichst hohe up-time besitzen, da die besten Prozeßergebnisse nichts nützen, wenn man nicht wirtschaftlich fertig en kann. (-z-