Random Matrix Theory Analysis of a Temperature-Related Transformation in Statistics of Fano–Feshbach Resonances in Thulium Atoms

Recently, the transformation from random to chaotic behavior in the statistics of Fano–Feshbach resonances was observed in thulium atoms with rising ensemble temperature. We performed random matrix theory simulations of such spectra and analyzed the resulting statistics in an attempt to understand the mechanism of the transformation. Our simulations show that, when evaluated in terms of the Brody parameter, resonance statistics do not change or change insignificantly when higher temperature resonances are appended to the statistics. In the experiments evaluated, temperature was changed simultaneously with optical dipole trap depth. Thus, simulations included the Stark shift based on the known polarizability of the free atoms and assuming their polarizability remains the same in the bound state. Somewhat surprisingly, we found that, while including the Stark shift does lead to minor statistical changes, it does not change the resonance statistics and, therefore, is not responsible for the experimentally observed statistic transformation. This observation suggests that either our assumption regarding the polarizability of Feshbach molecules is poor or that an additional mechanism changes the statistics and leads to more chaotic statistical behavior.     

KINETIC INVESTIGATION OF THE PHOTOLYSIS OF 2-OXO-2,5-DIHYDRO-1,3,4-OXADIAZOLES

Abstract. –A reaction scheme for the photolysis of 2-oxo-2,5-dihydro-1,3,4-oxadiazoles is given by kinetic analysis, quantum yield measurement and product determination. The different reaction pathways in acetonitrile and ether are discussed.     

Structure of radical cations of saturated heterocyclic compounds with two heteroatoms as studied by electron paramagnetic resonance, electron-nuclear double resonance, and density functional theory calculations

The radical cations of piperazine, morpholine, thiomorpholine, and thioxane were investigated by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy in a solid Freon matrix. Optimized geometry and magnetic parameters of the radical cations were calculated using a density functional theory (DFT)/Perdew-Burke-Ernzerhof (PBE) method. Both experimental and theoretical results suggest that all the studied species adopt chair (or distorted chair) conformations. No evidence for the boat conformers with intramolecular sigma-bonding between heteroatoms were obtained. In the cases of morpholine and thioxane, the oxygen atoms are characterized by relatively small spin populations, whereas a major part of spin density is located at N and S atoms, respectively. The thiomorpholine radical cation exhibits nearly equal spin population of N and S atoms. In most cases (except for thioxane), the calculated magnetic parameters agree with the experimental data reasonably well.     

Printable Magnetoelectronics

The field of printable electronics is well developed. A large variety of electronic components assembled as printable optoelectronic devices and communication modules are already available. However, the element responding to a magnetic field, which is highly demanded for the concept of printable electronics has only been realized very recently. A printable magnetic sensing device has been one of the remaining missing building blocks crucial to realize the concept of entirely printable electronics. Here, we position the novel topic of printable magnetic sensorics in a family of printable electronics and highlight possible application directions of this technology.     

Nucleophile‐electrophile interactions in the reaction of oxiranes with carboxylic acids in the presence of tertiary amines

The nucleophile‐electrophile interactions in the reaction system “N,N‐dimethylaniline – acetic acid – epichlorohydrin” have been investigated using kinetic methods and computer modeling. The observed orders of reactions have been determined for the overall reaction as well as for individual stages. The kinetic equations have been proposed; the activation parameters of the reactions have been evaluated. The behavior of the initial (amine) and intermediate (carboxylate) nucleophiles has been detailed in reaction pathway. Amine reacts with oxirane activated by acidic reagent while carboxylate‐anion—with both activated and nonactivated epichlorohydrin. The mechanism of oxirane ring opening by acid reagent in the presence of tertiary amine has been proposed, which comprise parallel‐consecutive compensation stages of reaction product formation. It has been demonstrated that the observed reaction order with respect to acid reactant depends upon the nature of electrophilic reagent (activated/nonactivated oxirane) and the ratio of the rates of compensation stages.     

Tin– and Titanium–Oxygen Nanostructures on the Various Hydr(oxides) Surfaces

Tin– and titanium–oxygen nanostructures were synthesized by molecular layer-by-layer deposition from the gaseous phase onto various substrates (SnO₂, SiO₂, AlOOH) using (in the course of synthesis) hydroxyl and methoxy surface groups. The electrokinetic (electrokinetic potential, isoelectric point) and adsorption (adsorption of potential-determining ions, the point of zero charge) properties of prepared composites were studied as a function of pH of NaCl background solutions. Synthesis conditions that make it possible to obtain (on the boehmite substrate) nanostructures with electrosurface characteristics similar to the properties of corresponding bulk oxides were determined.     

Kinetic isotope effect and mechanism of catalytic reaction of hydroxybenzenes with epichlorohydrin

Kinetic data are presented for catalytic reactions of 3-nitrophenol and 4,4′-dihydroxydiphenyl sulfone with epichlorohydrin. Magnitudes of the kinetic isotope effects have been determined for these reactions, and a mechanism of catalysis is proposed. Donetsk State University, 24 Universitetskaya ul., Donetsk 340055, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 302–305, September–October, 1998.     

Interferometric method to measure and test the optical homogeneity of transparent materials

The main idea of the method is to eliminate physically the influence of errors of glass sample plane surfaces on the wavefront transmitting through the sample. This makes it possible to reveal the “pure” optical inhomogeneity of the material independently of the errors of flat surfaces of a glass sample made in the form of a plane-parallel plate or a wedge of the small refractive angle. A basic optical layout of the laser interferometer explaining the capabilities of the practical application of the method is presented.     

Universal functions for estimating total vibration-rotation band absorptance—I. Linear molecules and spherical tops

We estimate total band absorptances and their derivatives for nonoverlapping lines of vibration-rotation bands for linear molecules and spherical tops. We use universal functions obtained by replacing the sums of line contributions by integrals over the rotational quantum numbers. An optical path is introduced for the total band. Only general information is utilized on vibrational transitions and line shapes. Power and asymptotic series have been obtained for Doppler and Lorentz line shapes. For a linear molecule and the Lorentz shape, approximate formulae have been derived for the universal functions.     

High energy proton ejection from hydrocarbon molecules driven by highly efficient field ionization

We investigated the ejection of energetic protons from a series of polyatomic hydrocarbon molecules exposed to 790 nm 27 fs laser pulses. Using multiparticle coincidence imaging we were able to decompose the observed proton energy spectra into the contributions of individual fragmentation channels. It is shown that the molecules can completely fragment already at relatively low peak intensities of a few 10(14) W/cm(2), and that the protons are ejected in a concerted Coulomb explosion from unexpectedly high charge states. The observations are in agreement with enhanced ionization taking place at many C-H bonds in parallel.