Fluorescence Spectral Properties of Methyl Orange in Homogeneous Media

Journal of Fluorescence - The methyl orange [C14H14N3SO3Na], an azo dye exhibited strong emission and large Stokes shift in various solvents, and the largest shift (Δλ = 125.51nm or...     

Scaling of x-ray emission and ion velocity in laser produced Cu plasmas

The x-ray emission from slab targets of copper irradiated by Nd:glass laser (1.054 μm, 5 and 15 ns) at intensities between 10¹² and 10¹¹W/cm² has been studied. The x-ray emissions were monitored with the help of high quantum efficiency x-ray silicon photo diodes and vacuum photo diodes, all covered with aluminium filters of different thickness. The x-ray intensity vs the laser intensity has a scaling factor of (1.2–1.92). The relative x-ray conversion efficiency follows an empirical relationship which is in close agreement with the one reported by Babonneau et al. The ion velocities were monitored using Langmuir probes placed at different angles and radial distances from the target position. The variation of the ion velocity with the laser intensity follows a scaling of the form Φ ^β where β ∼0.22 which is in good agreement with the reported scaling factor values. The results on the x-ray emission from Cu plasma are reported.     

Multiple charge states of titanium ions in laser produced plasma

An intense laser radiation (10¹² to 10¹¹ W/cm⁻²) focused on the solid target creates a hot (≥1 keV) and dense plasma having high ionization state. The multiple charged ions with high current densities produced during laser matter interaction have potential application in accelerators as an ion source. This paper presents generation and detection of highly stripped titanium ions (Ti) in laser produced plasma. An Nd:glass laser (KAMETRON) delivering 50 J energy (λ=0.53 μm) in 2.5 ns was focused onto a titanium target to produce plasma. This plasma was allowed to drift across a space of ∼3 m through a diagnostic hole in the focusing mirror before ions are finally detected with the help of electrostatic ion analyzer. Maximum current density was detected for the charge states of +16 and +17 of Ti ions for laser intensity of ∼10¹¹ W/cm⁻².     

The chiral potts model and its associated link invariant

A new link invariant is derived using the exactly solvable chiral Potts model and a generalized Gaussian summation identity. Starting from a general formulation of link invariants using edge-interaction spin models, we establish the uniqueness of the invariant for self-dual models. We next apply the formulation to the self-dual chiral Potts model, and obtain a link invariant in the form of a lattice sum defined by a matrix associated with the link diagram. A generalized Gaussian summation identity is then used to carry out this lattice sum, enabling us to cast the invariant into a tractable form. The resulting expression for the link invariant is characterized by roots of unity and does not appear to belong to the usual quantum group family of invariants. A table of invariants for links with up to eight crossings is given.     

Simultaneous synthesis of TiO2 microrods in situ decorated with Ag nanoparticles and their bactericidal efficiency

In this study, we report a simple and cost-effective method for in situ decoration of Ag NPs onto nanoporous TiO₂ microrods by one medium (ethylene glycol) that can produce two different morphologies. In order to investigate the morphology, phase composition, crystalline structure, and chemical state (valency) of samples before and after annealing in air at different temperatures, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed. The present results show that the size, morphology and crystallinity of both Ag NPs and TiO₂ microrod substrate depend on the post-annealing treatment temperatures. The annealed Ag–TiO₂ NP/microrod composites show large inhibition zones against E. coli bacteria. The obtained Ag–TiO₂ composites have the potential for use as a novel antibacterial material and in water treatment applications.     

Intense laser induced shock generation in gold targets

Abstract

Experiments carried out demonstrate the production due tosoft X-rays of enhanced ablation pressure. The targets used were planar gold foils. Aluminium targets were also used to demonstrate the relative effect.     

Internal heavy atom effect on the radiative and non-radiative rate constants in xanthene dyes

Flourescence quantum yield (ø_f), phosphorescence and fluorescence quantum yield ratio (ø_p/ø_f) and the observed triplet decay time (τ_po) of fluorescein and its halogen derivatives have been measured. On halogen substitution an increase in ø_p/ø_f and a decrease in ø_f and τ_po is observed in the sequence of Cl, Br, and I. The increase in ø_p/ø_f is not in the same proportion as the decrease in τ_po. Although ø_p/ø_f is higher for cations than for dianions, it increases more for dianions on halogen substitution. However, the increase in 1/τ_po is about 10³ times more for cations than for dianions. The radiative and non-radiative rate constants viz., k_is, k_p and k_qp have been calculated. On halogen substitution k_f remains almost constant, whereas an increase in k_p, k_is and k_qp is observed. For dianions the increase occurs in the order k_qp> k_is> k_p while for cations the order is k_qp> k_p> k_is. The deuterium solvent effect on triplet decay time and intensity is also observed.     

Capillary zone electrophoresis in phosphate buffer--known or unknown?

It has been shown recently that the analysis records in capillary electrophoresis may involve regions with extremely strong electromigration dispersion of peaks. Such a fundamental effect is due to the existence of more centers of symmetry in a given electrolyte system. This paper shows that even such a simple and frequently used electrolyte system as phosphate buffer may exhibit more than one center of symmetry. By using the peak shape diagram approach we have revealed that neutral and alkaline phosphate buffers have two centers of symmetry and one center of extreme dispersion. Model experiments confirmed this new important discovery.