Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Kinetics and mechanism of decomposition of intermediate complex during oxidation of pectate polysaccharide by potassium permanganate in alkaline solutions

The kinetics of decomposition of an [Pect·Mn^VIO₄^2?] intermediate complex have been investigated spectrophotometrically at various temperatures of 15–30°C and a constant ionic strength of 0.1 mol dm^?3. The decomposition reaction was found to be first‐order in the intermediate concentration. The results showed that the rate of reaction was base‐catalyzed. The kinetic parameters have been evaluated and found to be ΔS^≠ = ? 190.06 ± 9.84 J mol^?1 K^?1, ΔH^≠ = 19.75 ± 0.57 kJ mol^?1, and ΔG^≠ = 76.39 ± 3.50 kJ mol^?1, respectively. A reaction mechanism consistent with the results is discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 67–72, 2003     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

Analysis of a shielded TE011 mode composite dielectric resonator for stable frequency reference

Analysis of a TE₀₁₁ mode composite sapphire-rutile dielectric resonator has been carried out to study the temperature variation of resonance frequency, close to the Cs atomic clock hyperfine frequency of 9.192 GHz. The complementary behavior of dielectric permittivity with temperature of the composite has been exploited to obtain the desired turning point in the resonant frequency. The frequency of the composite structure is found to be independent of the shield diameter beyond four times the puck diameter.     

Fabrication and characterization of bimetallic Pt-Au nanowires supported on FSM-16 and their catalytic activities toward water-gas shift reaction

A facile, previously unexplored, method to synthesize bimetallic Pt-Au nanowires (20nm diameter×120-170nm long) on mesoporous FSM-16 (2.7nm) was fabricated by co-impregnation of H(2)PtCl(6) with HAuCl(4) followed by evacuation at 300K and finally exposure to the CO/H(2)O gas mixture (60:5Torr) at 323K for 1.0h. On the other hand, spherical monometallic nanoparticles of pure Pt (7.0nm diameter) and Au (7-26nm diameter) were synthesized as well, by impregnation, at the same reaction conditions. The catalysts were characterized by in situ FTIR spectroscopy, UV-vis absorption spectroscopy, TEM, TPR and TPCOR. The catalytic activities toward the water-gas shift reaction (WGSR) were also examined under atmospheric pressure and at the margin of 323-373K. The optical absorption spectra showed a remarkable shift and broadening of Pt-Au surface Plasmon resonance band at 515nm apart from those of individual analogue emphasizing bimetallic formation. Results from in situ FTIR spectroscopy indicated that incorporation of Au assisted and stabilized the formation of carbonyl clusters of Pt-Au-CO (2084cm(-1)) and Pt-CO (1888cm(-1)) inside the host FSM-16. The Pt-Au carbonyl clusters built up at the moment of vanishing the linear carbonyl band of the charged Au (Au(+)-CO, 2186cm(-1)) along with a concomitant increase in the reduced gold (Au(0)-CO, 2124cm(-1)) species. TPR profiles showed that the H(2) consumed was higher for Pt/FSM-16 than for Pt-Au/FSM-16 verifying the facile reduction of Pt moieties after addition of Au. The CO adsorption peak maximum, in TPCOR, for Pt/FSM-16 occurred at higher temperature than that of Pt-Au/FSM-16, which exhibited higher amounts of CO(2) produced. The relative decrease in CO bindings on bimetallic surface was responsible for increasing the CO oxidation activity mainly through an association mechanism. Accordingly, the activity of Pt-Au/FSM-16 towards WGS showed a marked increase (8-23 times) compared with those of monometallics emphasizing the dependence of this reaction on the electronic defects of the nanowires. A straightforward reduction mechanism was deduced for Pt-Au alloy formation in view of the results obtained.     

Physicochemical studies on cross-linked thorium(IV)–alginate complex especially the electrical conductivity and chemical equilibrium related to the coordination geometry

The electrical conductivity of cross-linked thorium(IV)–alginate complex in the form of circular disc has been investigated as a function of temperature. The Arrhenius plot of log σ vs. 1/T showed a simple parabolic shape at the early stages, followed by a sharply increase in o values with raising the temperature at the final stages. This behaviour was interpreted by the formation of free-radicals at the initial stages, followed by the degradation of the complex at elevated temperatures to give rise to thorium oxide product. The heterogeneous chemical equilibrium for exchange of Th⁴⁺ counter ions in the complex by H⁺ ions has been investigated by titrimetric and complexometric techniques. The thermodynamic equilibrium constant was found to be 26 ± 0.25 dm⁹ mol^?3 at 25 °C. The X-ray diffraction pattern indicated that thorium(IV)–alginate complex is amorphous in nature. Infrared absorption spectra indicated that Th⁴⁺ is chelated to alginate macromolecular chains and displayed υ_s OCO^? and υ_as OCO^? in the ranges of 1419 and 1635 cm^?1, respectively. A geometrical structure for chelation of thorium(IV) to the functional groups of alginate macromolecule is suggested and discussed in terms of complex stability.     

Photochromism of tetrahydroindolizines. Part XIV: synthesis of cis-fixed conjugated photochromic pyridazinopyrrolo[1,2-b]isoquinolines incorporating carbon-rich linkers

New carbon-rich photochromic tetrahydroindolizines (THIs) bearing dihydroisoquinoline derivatives as heterocyclic bases (region B) have been synthesized via different chemical and photochemical pathways. Three alternative pathways for the synthesis of the target photochromic THI-based pyridazinopyrrolo[1,2-b]isoquinolines via in situ trapping with hydrazine hydrate have been established. In order to obtain high product yields, different Sonogashira-mediated coupling reactions have been optimized. Low temperature multichannel UV–vis and flash photolysis techniques were used to detect the photochromic and kinetic properties of the synthesized system.     

Kinetics and mechanism of the non-isothermal decomposition: I. Some divalent cross-linked metal-alginate ionotropic gels

The kinetics of thermal decomposition of Sn(II), Pb(II), Cd(II) and Hg(II) alginate gels have been studied using thermogravimetry (TG) and derivative thermogravimetry (DTG) in static air. The thermal dehydration of each gel complex was found to occur in one step, whereas the decomposition of the dehydrated complexes occurred in two steps. The kinetic parameters were computed by different models and a tentative decomposition mechanism consistent with the kinetic observations is discussed.This revised version was published online in November 2005 with corrections to the Cover Date.