Scanning tunneling lithography of silicon nanoparticle films

Monolayer and bi-layer silicon nanoparticle (SiNP) films with wide band gaps (up to 4 eV) have been produced in UHV with narrow size distributions of particles with 2-4 nm diameters and were studied using scanning tunneling microscopy (STM) and spectroscopy (STS). The films then were manipulated by applying different values for the tunneling resistance. Nanoparticle fusion and fission processes allow to shape the particles in the films in various ways and to write in white and black on the film template.     

Notations, Spectroscopic Parameters, Energy Levels and Their Relationship to Effective Hamiltonian Formalism of Diatomic Molecules

This paper presents a part of the culmination of the collective efforts in developing a cohesive and consolidated enunciation of the spectroscopic parameters and their relationship to effective molecular Hamiltonians for diatomic formalism, linear four-atomic formalism and quasi-linearity, Watson Hamiltonian and the complexities in symmetric and asymmetric top spectral structures. All these considered together present a beautiful and consistent picture of molecular spectroscopy. In this paper we deal with the diatomic formalism. This paper forms our tribute to Professor K. Narahari Rao and in the second part of the paper we convoy our gratitude to him with a summary of his more than half century of work and an obituary. We will deal with other forms of molecular species which will be connected to optical pumping and/or interstellar space.     

Density functional calculations for shell closures in Mg clusters

Motivated by recent measurements on Mg clusters we discuss the electronic structure and shell closures of these type of systems in the framework of self-consistent mean fields derived from density-functional theory. The ionic background is treated at different levels of refinement: spherical jellium model, and the spherically-averaged-pseudo-potential scheme (SAPS) with local as well as non-local pseudo-potentials. The ionic positions in SAPS are optimized using a Metropolis simulated annealing. It is shown that the details of ionic background influence sensitively the electronic levels sequence near the Fermi energy. In particular, the non-local effects from the pseudo-potential change the relations between states with high and with low angular momentum. Some of these effects go into the right direction towards experiment. Received 3 July 2001 and Received in final form 29 October 2001     

N-doping and coalescence of carbon nanotubes: synthesis and electronic properties

Self-assembly pyrolytic routes to large arrays (<2.5 cm²) of aligned CN_x nanotubes (15–80 nm OD and <100 μm in length) are presented. The method involves the thermolysis of ferrocene/melamine mixtures (5:95) at 900–1000 °C in the presence of Ar. Electron energy loss spectroscopy (EELS) reveals that the N content varies from 2–10%, and can be bonded to C in two different fashions (double-bonded and triple-bonded nitrogen). The electronic densities of states (DOS) of these CN_x nanotubes, using scanning tunneling spectroscopy (STS), are presented. The doped nanotubes exhibit strong features in the conduction band close to the Fermi level (0.18 eV). Using tight-binding and ab initio calculations, we confirm that pyridine-like (double-bonded) N is responsible for introducing donor states close to the Fermi Level. These electron-rich structures are the first example of n-type nanotubes. Finally, it will be shown that moderate electron irradiation at 700–800 °C is capable of coalescing single-walled nanotubes (SWNTs). The process has also been studied using tight-binding molecular dynamics (TBMD). Vacancies induce the coalescence via a zipper-like mechanism, which has also been observed experimentally. These vacancies trigger the organization of atoms on the tube lattices within adjacent tubes. These results pave the way to the fabrication of nanotube heterojunctions, robust composites, contacts, nanocircuits and strong 3D composites using N-doped tubes as well as SWNTs. Received: 10 October 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

An alternative approach for microlithography light source

A hybrid master oscillator–power amplifier (hybrid MOPA) scheme is proposed as a microlithography light source. The seed pulses are generated in the visible spectral range—where the necessary spectral purity is more easily achieved—and after frequency conversion are amplified in an excimer amplifier. The new concept enables us to decrease the bandwidth considerably, approaching the theoretical limit posed by the uncertainty relation. The feasibility of the new approach is demonstrated by a dye/excimer MOPA system, generating deep ultraviolet DUV (248-nm) pulses of 0.2-pm bandwidth.     

Beam-helicity asymmetry in photon and pion electroproduction in the Δ(1232)-resonance region at Q2 = 0.35(GeV/c)2

The beam-helicity asymmetry has been measured simultaneously for the reactions p→epγ and p→epπ ⁰ in the Δ(1232)-resonance region at Q ² = 0.35(GeV/c)². The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on dispersion relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some γ ^(*) N→πN multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels (γ and π ⁰) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization.     

Efficient Synthesis of Pyrrolo[1,2-f]phenanthridine Derivatives via Dipolar Cycloaddition of Phenanthridine,Activated Acetylenes,and Ethyl Bromopyruvate

The three-component reactions of phenanthridine, activated acetylenes, and ethyl bromopyruvate through both of simultaneous and stepwise process are surveyed. The reactions afforded the corresponding pyrrolo[1,2-f]phenanthridine derivatives in good yields without using any catalyst and activation.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Off-on-off luminescent switching of a dye containing imidazo[4,5-f][1,10]phenanthroline

A new acid-base fluorescent switch containing both imidazo[4,5-f][1,10]-phenanthroline and triphenylamine groups has been synthesized.Its fluorescence emissions and absorptions can be reversibiy changed through protonation/deprotonation of imidazole and amine moiety by controlling the intramolecular charge transfer(ICT) process,leading to off-on-off fluorescent molecular switching.     

Orlicz Figà – Talamanca Herz algebras and invariant means

The aim of this paper is to initiate a systematic study of the Orlicz Figà – Talamanca Herz algebras on locally compact groups. We also introduce and study invariant means on the dual of these algebras.     

Electronic Emission from Hg-Atoms and HgCl-Radicals Due to Collisions of Nitrogen Ions and HgCl2/Hg2Cl2 Molecules

Emission spectra of the (B-X), (C-X) and (D-X) band systems of HgCl-radical and mercury atomic lines from highly excited levels to various lower levels have been observed during collisions of N⁺ and N⁺ ₂ ions and HgCl₂/Hg₂Cl₂ molecules at different laboratory kinetic energies of the projectile ions. Emission cross-sections of the most intense mercury atomic lines and the (C-X) band system of the HgCl-radicals, have been measured in the laboratory kinetic energy range of 100–900 eV.