Interferometric technique for measuring broadband ultrashort pulses at the sampling limit

We present a new technique for measuring ultrashort optical pulses by use of spectral phase interferometry for direct electric-field reconstruction that is suitable for large bandwidth pulses. The method does not require generation of a replica of the pulse to be measured and encodes the spectral phase information in a spatial interference pattern. A major advantage of this method is that the spectral sampling saturates the Whittaker-Shannon bound. Moreover, the technique allows for the characterization of some types of space-time coupling. An experimental demonstration of the technique is presented.     

Heats of displacement of hydrogen from palladium by noble gases

It has been observed that noble gases, such as helium, neon and argon produce heat evolution when contacted with Pd powder partially saturated with hydrogen. These phenomena have been studied with flow-through adsorption microcalorimetry. The observed exothermic effects are comparable to those usually associated with the heat of sorption of hydrogen in palladium. It is suggested that the noble gases displace the adsorbed H species from the surface of Pd, causing their reabsorption in the Pd lattice with the exothermic heat of PdH bonds formation, or the formation of H₂, both heat evolutions being observed with a flow-through microcalorimeter.     

Numerical study of light correlations in a random medium close to the Anderson localization threshold

We applied a finite-difference time domain algorithm to the study of field and intensity correlations in random media. Close to the onset of Anderson localization, we observe deviations of the correlation functions, in both shape and magnitude, from those predicted by the diffusion theory. Physical implications of the observed phenomena are discussed.     

Analysis of Phosphorescence Decay in Heterogeneous Systems: Consequences of Finite Excitation Flash Duration

Analysis of phosphorescence lifetimes using the Stern-Volmer equation is a reliable means of determining quencher concentration for a uniform sample. Methods of analysis for heterogeneous systems are based on the assumption that the excitation is produced by a momentary flash. This condition is an idealization because a real flash has a finite duration and a complex time profile. In the case of a heterogeneous quencher concentration, an excitation flash produces different initial intensities and different times of peak intensity from compartments having different concentrations of quencher. We formulated a model to explore the effects of flash duration on the shape of the emission curve obtained from systems in which the heterogeneity is continuous. We developed mathematical models that can be used to recover fitting parameters of continuous distributions of reciprocal lifetimes approximated as rectangular or Gaussian distributions, or an arbitrary histogram. We also formulated a procedure to convert the distribution of reciprocal lifetimes into a volume distribution of quencher concentration. We found that (1) the Stern-Volmer ratio of phosphorescence intensities cannot be employed for interpretation of pulse phosphorometric data in terms of a volume distribution of quencher; (2) shortening the flash duration decreases the difference of initial intensities between compartments having high and low quencher concentration; (3) the parameters of the volume distribution of quencher concentration can be recovered correctly only after taking account of the difference in initial intensities; and (4) calibration of the initial intensities for a given fitting delay and flash function is necessary.     

On spherical expansions of zonal functions on Euclidean spheres

This paper describes a new approach to the problem of computing spherical expansions of zonal functions on Euclidean spheres. We derive an explicit formula for the coefficients of the expansion expressing them in terms of the Taylor coefficients of the profile function rather than (as done usually) in terms of its integrals against Gegenbauer polynomials. Our proof of this result is based on a polynomial identity equivalent to the canonical decomposition of homogeneous polynomials and uses only basic properties of this decomposition together with simple facts concerning zonal harmonic polynomials. As corollaries, we obtain direct and apparently new derivations of the so-called plane wave expansion and of the expansion of the Poisson kernel for the unit ball. Received: 26 January 2007     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Reaction of 2-trifluoroacetyl-1,8-Bis(dimethylamino)naphthalene with strong organic bases: Deprotonation of 1-NMe2 group resulting in the formation of Benzo[g]indole derivatives versus nucleophilic addition to CO group

A novel approach to pyrrole ring closure in 2-trifluoroacetyl- and 2-ethoxycarbonyl-1,8-bis(dimethylamino)naphthalenes via treatment with 2-lithium-1,8-bis(dimethylamino)naphthalene producing the corresponding benzo[g]indole derivatives, was examined with different alkyl- and aryllithium compounds as well as with LDA. It was found that the highest yields of benzo[g]indoles (up to 70%) are obtained with aryllithium reagents when they contain NMe₂ group in ortho-position to the carbanionic centre. In all other cases the formation of acyclic alcohol arising from ordinary intermolecular addition of the carbanion to the CO group strongly prevails. The dramatic facilitation of deprotonation of the N-Me group in substrate followed by pyrrolic cyclization in the case of 2-lithium-N,N-dimethylanilines was explained through a specific structure of the reaction transition state.     

Ergodic properties of anomalous diffusion processes

In this paper we study ergodic properties of some classes of anomalous diffusion processes. Using the recently developed measure of dependence called the Correlation Cascade, we derive a generalization of the classical Khinchin theorem. This result allows us to determine ergodic properties of Lévy-driven stochastic processes. Moreover, we analyze the asymptotic behavior of two different fractional Ornstein–Uhlenbeck processes, both originating from subdiffusive dynamics. We show that only one of them is ergodic.     

The formation of oxide nanoparticles on the surface of natural clinoptilolite

Nanoparticles of NiO, ZnO and Cu₂O crystallize when the Ni-, Zn- and Cu-exchanged natural clinoptilolite, respectively, are dehydrated by heating in air at 550 °C. The dehydration of Mn-exchanged clinoptilolite does not lead to the crystallization of manganese oxide but affects the crystallinity of the host clinoptilolite lattice, which becomes amorphous. The NiO, ZnO and Cu₂O nanoparticles are found to be randomly dispersed in the clinoptilolite matrix. The particle size varies from 2 to 5 nm and exceeds the aperture of the clinoptilolite channel (approximately 0.4 nm), suggesting that the crystallization of the oxide phases takes place on the surfaces of clinoptilolite microcrystals.