Iridium/silicon multilayers for extreme ultraviolet applications in the 20-35 nm wavelength range

We have developed an Ir/Si multilayer for extreme ultraviolet (EUV) applications. Normal incidence reflectance measurements of a prototype film tuned to 30 nm wavelength show superior performance relative to a conventional Mo/Si multilayer structure; we also find good stability over time. Transmission electron microscopy and electron dispersive x-ray spectroscopy have been used to examine the microstructure and interface properties of this system: we find amorphous Si layers and polycrystalline Ir layers, with asymmetric interlayer regions of mixed composition. Potential applications of Ir/Si multilayers include instrumentation for solar physics and laboratory EUV beam manipulation.     

Temperature-dependent modulation by biaryl-based monomers of the chain length and morphology of biphenyl-based supramolecular polymers

Supramolecular copolymerizations offer attractive options to introduce structural and functional diversity in supramolecular polymer materials. Yet, general principles and structure–property relationships for rational comonomer design remain lacking. Here, we report on the supramolecular (co)aggregation of a phenylpyridine and bipyridine derivative of a recently reported biphenyl tetracarboxamide-based monomer. We show that both arylpyridines are poor monomers for supramolecular homopolymerizations. However, the two arylpyridines efficiently influence supramolecular polymers of a biphenyl-based polymer. The phenylpyridine derivatives primarily sequestrate biphenyl monomers, while the bipyridine intercalates into the polymers at high temperatures. Thereby, these two poorly homopolymerizing monomers allow for a fine control over the length of the biphenyl-based supramolecular polymers. As such, our results highlight the potential to control the structure and morphology of supramolecular polymers by tailoring the electronic properties of additives.

Supramolecular copolymerizations offer attractive options to introduce structural and functional diversity in supramolecular polymer materials.     

Correlated displacement-T2 MRI by means of a Pulsed Field Gradient-Multi Spin Echo Method

A method for correlated displacement-T2 imaging is presented. A Pulsed Field Gradient-Multi Spin Echo (PFG-MSE) sequence is used to record T2 resolved propagators on a voxel-by-voxel basis, making it possible to perform single voxel correlated displacement-T2 analyses. In spatially heterogeneous media the method thus gives access to sub-voxel information about displacement and T2 relaxation. The sequence is demonstrated using a number of flow conducting model systems: a tube with flowing water of variable intrinsic T2's, mixing fluids of different T2's in an "X"-shaped connector, and an intact living plant. PFG-MSE can be applied to yield information about the relation between flow, pore size and exchange behavior, and can aid volume flow quantification by making it possible to correct for T2 relaxation during the displacement labeling period Delta in PFG displacement imaging methods. Correlated displacement-T2 imaging can be of special interest for a number of research subjects, such as the flow of liquids and mixtures of liquids or liquids and solids moving through microscopic conduits of different sizes (e.g., plants, porous media, bioreactors, biomats).     

Terbium-based extreme ultraviolet multilayers

We have fabricated periodic multilayers that comprise either Si/Tb or SiC/Tb bilayers, designed to operate as narrowband reflective coatings near 60 nm wavelength in the extreme ultraviolet (EUV). We find peak reflectance values in excess of 20% near normal incidence. The spectral bandpass of the best Si/Tb multilayer was measured to be 6.5 nm full width at half-maximum (FWHM), while SiC/Tb multilayers have a more broad response, of order 9.4 nm FWHM. Transmission electron microscopy analysis of Si/Tb multilayers reveals polycrystalline Tb layers, amorphous Si layers, and relatively large asymmetric amorphous interlayers. Thermal annealing experiments indicate excellent stability to 100 degrees C (1 h) for Si/Tb. These new multilayer coatings have the potential for use in normal incidence instrumentation in a region of the EUV where efficient narrowband multilayers have not been available until now. In particular, reflective Si/Tb multilayers can be used for solar physics applications where the coatings can be tuned to important emission lines such as O V near 63.0 nm and Mg X near 61.0 nm.     

Electronic structure of Li− and F− calculated directly in momentum space

Summary A self-consistent field method is applied to compute directly in momentum space the electronic structures of the bound anions Li^– and F^– at the Hartree-Fock level. The convergence towards the Hartree-Fock limit, starting from STO-3G, 3–21G, 3–21+G and 6–311+G AO's, is stable and monotonous. Substantial improvement in the quality of the anion orbitals is noted already after one iteration. Particularly interesting is the efficiency with which the method modifies and improves the shape of the trial functions.     

Metal Complexes of Functionalized Sulfur‐Containing Ligands. Part XIX

The title compounds were prepared starting from the dihydropyrrolones 4 – 6 . Nucleophilic displacement and ring closure yielded the 1H‐pyrrolo[3,2‐c]isothiazol‐5(4H)‐ones 8 and 10 . The fused systems formed salts with strong acids and electrophiles ( 15, 16 ), as well as with bases. Oxidation led either to S(2)‐oxides ( 18a, 20a ) or to the corresponding bicyclic sultams ( 18b, 20b ), depending on the reaction conditions. The sulfinamide 18a was also obtained from the known 1,2‐dithiolopyrrolone S‐oxide 21 by a ring‐opening/ring‐closure reaction sequence. O‐Methylation of 8 furnished the ‘azafulvene' 17 . The oxidative addition of [Pt(η²‐C₂H₄)L₂] ( 24a : L=Ph₃P, 24b : L=1/2 dppf, 24c : L=1/2 (R,R)‐diop) to 18a and 20a led to the cis‐amido‐sulfenato Pt complexes 25 and 26a – c , respectively.     

Comments on the topic “computation of large molecules”

Quantum chemical and molecular modeling computations on large molecular systems are defined for the computational facilities assumed to be available from now to the next 4 years. We considered a few topics which are requiring much attention. The correlation energy is discussed in some detail and we have presented two new functionals, called the J-functional and the K-functional, which make use of Coulomb or exchange-type integrals. In addition, we report new computational results for the Coulomb-Hole-Hartree-Fock approximation. Very brief summaries on new developments in relativistic Dirac-Fock computation and in density functional theory, on the advantages gained by using different basis sets in the same computation, and on the promises of parallel computing conclude the article. © 1996 John Wiley & Sons, Inc.     

Variation–iteration method in momentum space: Determination of Hartree–Fock atomic orbitals

A method using the Svartholm iterative procedure to solve atomic Hartree–Fock equations in momentum space is defined and applied to the ground states of Be and B⁺. The calculated atomic orbital properties follow a monotonic and stable convergence, but with rates of convergence depending on each property. The evolution of the orbitals during the iterations is explained by the combined actions of the variational principle, the Svartholm iterative procedure, and the momentum space representation. © 1993 John Wiley & Sons, Inc.