Plasmonics – the missing link between nanoelectronics and microphotonics

Plasmonics is an exciting new device technology that has recently emerged. It exploits the unique optical properties of metallic nanostructures to enable routing and manipulation of light at the nanoscale. A tremendous synergy can be attained by integrating plasmonic, electronic, and conventional dielectric photonic devices on the same chip and taking advantage of the strengths of each technology. We will provide a perspective on future directions and possibilities for integrating plasmonic devices on a Si chip. PACS 42.82.-m; 42.82.Ds     

Oscillator strength measurements of the 3p ↦ nd Rydberg transitions of sodium

We report new measurements of the oscillator strengths of the 3p ²P_3/2 ↦nd ²D_{5/2, 3/2} and 3p ²P_1/2 ↦ nd ²D_3/2 Rydberg transitions of sodium using a thermionic diode ion detector in conjunction with the Nd:YAG pumped dye lasers. The ns ²S_1/2 and nd ²D_5/2,3/2 Rydberg series have been recorded via two-step excitation, from the 3p ²P_3/2 and 3p ²P_1/2 intermediate states. Employing the saturation technique, the photoionization cross sections from the 3p ²P_3/2 and 3p ²P_1/2 intermediate states at the first ionization threshold are determined as 7.9(1.3) Mb and 6.7(1.1) Mb respectively. The f-values of the Rydberg transitions are calibrated with the photoionization cross section measured at the first ionization threshold and compared with the earlier data.     

Microstructural studies of nanocrystalline α-alumina powder produced from Al13-cluster

Nanocrystalline alumina powder was produced from calcinations of Al₁₃-oxalate precipitates at 1100 °C. A nearly normal distribution of agglomerated alumina powder was obtained with an average particle size of about 1 μm. XRD measurement confirmed that the alumina produced was of high purity and crystalline α-phase. Microstructural features of both the precipitates and alumina obtained were studied using the small angle neutron scattering (SANS) technique. SANS examinations show the formation of microstructures in the alumina powder of mass fractals type with dimension of ∼2.8 indicative of low intra-granular porosity.     

Solvent effect on optical properties of hydrated lanthanide tris-acetylacetone

We have studied the optical absorption spectra of trivalent lanthanide(III) β-diketones. The enhancement in intensity of the hypersensitive transitions of Eu(III) ⁵D₀→⁷F₂ and Tb(III) ⁵D₄→⁷F₅ and ⁵D₄→⁷F₂ complexes was observed in various solution mediums. The oscillator strength for the intraconfigurational transitions has been determined using Judd-Ofelt theory. The change in the oscillator strength and band shape with respect to solvent type is rationalized in terms of ligand (solvent) structure and coordination properties. The intensity of hypersensitive transitions is found to be highly influenced in DMF solution. Electronic spectral studies of the Pr(III) and Nd(III) complexes in different solvents, which differ with respect to donor atoms, reveal that the chemical environment around the lanthanide ion has great impact on f-f transitions and any change in the environment in terms of solvent results in modifications of the spectra.     

Measurement of asymmetric optical pumping of ions accelerating in a magnetic-field gradient

We report observations of asymmetric optical pumping of argon ions accelerating in a magnetic-field gradient. The signature is a difference in the laser-induced-fluorescence emission amplitude from a pair of Zeeman-split states. A model that reproduces the dependence of the asymmetry on magnetic-field and ion-velocity gradients is described. With the model, the fluorescence intensity ratio provides a new method of measuring ion collisionality. This phenomenon has implications for interpreting stellar plasma spectroscopy data which often exhibit unequal Zeeman state intensities.     

Origins of boat or chair preferences in the Ireland-Claisen rearrangements of cyclohexenyl esters: a theoretical study

The relative energies of the chair and boat transition states of a variety of Ireland-Claisen rearrangements were obtained by B3LYP/6-31G calculations. Theoretical results are in good agreement with experimental data and provide a quantitative analysis of the origins of boat preferences that are observed in some of these reactions.     

Spectrophotometric determination of clotrimazole and Phenylephrine-HCl in pharmaceutical formulation using 1, 2-naphthoquinone-4-Sulphonic acid sodium salt (NQS) as a chromogenic reagent

A sensitive, rapid and economical spectrophotometric method based on their interaction with NQS reagent in basic medium, which produces orange-colored complexes, has been devised to identify many drugs with amino groups (clotrimazole and phenylephrine-HCl). The maximum absorption for the complexes of clotrimazole and phenylephrine-HCl is 455 and 484 nm, respectively. Beer's law is applicable in the concentration ranges of (2–40) μg/ml for clotrimazole and (0–20) μg/ml for phenylephrine-HCl. The molar absorptivity values are 3931.1760 L/mol.cm and 4521.4074 L/mol.cm of clotrimazole and phenylephrine-HCl respectively with accuracy of 100.0285%–103.1456% and RSD better than 3.3211%. The method has been successfully used to determine these medications in pharmaceutical formulations, and it has been found to be superior to British Pharmacopeia standard procedures. At a 95% confidence level, F and t-tests are less than the tabulated values.     

Electron acoustic solitary waves in unmagnetized nonthermal plasmas

Electron acoustic(EA) solitary waves(SWs) are studied in an unmagnetized plasma consisting of hot electrons(following Cairns-Tsalli distribution), inertial cold electrons, and stationary ions.By employing a reductive perturbation technique(RPT), the nonlinear Korteweg–de Vries(KdV) equation is derived and its SW solution is analyzed. Here, the effects of plasma parameters such as the nonextensivity parameter(q), the nonthermality of electrons(α), and the cold-to-hot electron density ratio(β) are investigated.