Recombination processes related to Eu2+ energy level position in ionic CaxCd1-xF2 crystals

Abstract

We study efficiency of autoionization and recombination transitions for europium in Ca_xCd_1-xF₂ host lattice depending on the energy level position of Eu²⁺ 4f⁶5d¹(e) excited states in respect to the conduction band (CB) states. From photoluminescence (PL) and absorption measurements we conclude that for x in the range of 1 - 0.65 thermalization within the 4f⁶5d¹(e) multiplet is faster than the appropriate autoionization transition. For x > 0.65, when all the excited 4f⁶5d¹ states are degenerate with the CB autoionization is immediate, Eu²⁺ intra-ion emission is quenched and a new Eu-related emission appears, which we tentatively assign to a radiative capture emission of hot nonequilibrium electrons.     

QED bremsstrahlung in decays of electroweak bosons

Isolated lepton momenta, in particular their directions are the most precisely measured quantities in pp collisions at LHC. This offers opportunities for multitude of precision measurements. It is of practical importance to verify if precision measurements with leptons in the final state require all theoretical effects evaluated simultaneously or if QED bremsstrahlung in the final state can be separated without unwanted precision loss. Results for final-state bremsstrahlung in the decays of narrow resonances are obtained from the Feynman rules of QED in an unambiguous way and can be controlled with a very high precision. Also for resonances of non-negligible width, if calculations are appropriately performed, such separation from the remaining electroweak effects can be expected. Our paper is devoted to validation that final-state QED bremsstrahlung can indeed be separated from the rest of QCD and electroweak effects, in the production and decay of Z and W bosons, and to estimation of the resulting systematic error. The quantitative discussion is based on Monte Carlo programs PHOTOS and SANC, as well as on KKMC which is used for benchmark results. We show that for a large class of W and Z boson observables as used at LHC, the theoretical error on photonic bremsstrahlung is 0.1 or 0.2 %, depending on the program options used. An overall theoretical error on the QED final-state radiation, i.e. taking into account missing corrections due to pair emission and interference with initial state radiation is estimated respectively at 0.2 % or 0.3 % again depending on the program option used.     

Double thioalkylation/arylation of nitroarenes with the reduction of nitro- to amino group

Some active bicyclic nitroarenes readily react with an excess of alkyl/arylthiols in the presence of DBU and bis-trimethylsilylacetamide (BSA) in DMF solution, to give dithioalkyl/aryl substituted anilines in moderate to good yields via displacement of ortho- and para-hydrogen atoms with simultaneous reduction of the nitro- to amino-group.     

Complexity principle of extremality in evolution of living organisms by information-theoretic entropy

We consider evolution from a multiorgan (multistage) organism, which has a number of identical organs (e.g. a trilobite with many pairs of legs), to another organism, which has one organ modified (specialized) into a different part of the body (e.g. claws of a crab) at the expense of reduction in the number of non-modified organs. We observe that in early stages of evolution multiple organs (pairs of legs) may be created, and that extra organs may rapidly be reduced during later stages. We ask: Why do extra organs evolve during early stages of evolution? To answer the question we construct and then analyze a simple although basic model of evolution based on information-theoretic entropy. We show that an extremality principle is valid in which the increase in number of identical organs is led by the gradient of information entropy increasing with the number of these organs. On the other hand, the reduction in number of these organs, observed for later stages of evolution, results from catastrophes between submanifolds of evolution, the surfaces on which modifications (specializations) of organs may occur. Our conclusion is that modification (specialization) of organs, while in principle consistent with the entropy principle of extremality, may lead evolution to a region of catastrophes, and that these catastrophes may explain extinction of some species. The same mathematical model is applied for explanation of parallel evolution of animals and for some evolution problems of flowers.     

Novel class of saccharide-based organogelators: glucofuranose derivatives as one of the smallest and highly efficient gelators

Gluco- and allofuranose derivatives, having unprotected three OH groups, were investigated as potential gelators, showing high gelating ability for a variety of organic solvents and result in new consistent class of organogelators. The minimum gelator concentration reaches 0.03%, which is one of the lowest concentrations achieved so far. The correlation between the saccharide crystal structure and its gelating ability was also examined. The SEM pictures of xerogeles obtained from concentrated and diluted gels (1.0-0.03%) show significant differences in μm-scale structure.     

Geometry of real polynomial mappings

In this paper we study the set of points at which a real polynomial mapping is not proper. Received: 7 May 1999; in final form: 18 September 2000 / Published online: 25 June 2001     

On ramification values of a polynomial mapping

 Let be affine algebraic varieties of dimension n-1. There is a proper polynomial mapping such that the set of its ramification values contains hypersurfaces , which are birationally equivalent to Received: 21 December 2001 Mathematics Subject Classification (2000): 14 D 06, 14 Q 20     

Properties of prealmost α-continuous and presemi-weakly continuous functions

Some properties of two classes of functions (p.a.α.c. and p.s.w.c) are studied. This revised version was published online in June 2006 with corrections to the Cover Date.     

The millimeter- and submillimeter-wave spectrum of the trans-gauche conformer of diethyl ether

The results of a first investigation of the rotational spectrum of the trans-gauche conformer of diethyl ether are reported. Two spectrometers have been used to measure the spectrum in the millimeter-wave and submillimeter-wave regions and a total of 1090 absorption line frequencies in the range 108-366 GHz were obtained and analyzed. Of these lines, 902 were measured with a spectrometer employing the fast scan submillimeter spectroscopic technique (FASSST) at Ohio State and the remaining 188 were measured with the phase-lock two-loop system (PLL) in Warsaw. The spectrum was fit to within experimental accuracy with the use of the A-reduced Watson Hamiltonian. Based on relative intensity measurements, the percentage of diethyl ether at room temperature in the trans-gauche conformer was found to be 30.5(13)%, in good agreement with prior spectroscopic values and an ab initio determination based on an energy difference of 5.40 kJ mol⁻¹ (452 cm⁻¹) between the excited trans-gauche and ground trans-trans conformers. This work also stimulated a critical evaluation of the data acquisition and calibration procedure of the FAAAST spectrometer, the results of which will be discussed.