High-spin two-quasiparticle bands in76Br

Excited states of the doubly-odd nucleus V6Br have been studied with in-beam γ-ray spectroscopy techniques. In addition to the positive parity band that has been extended up to I=(13) a I^π=4^? isomer (T_1/2=0.5±0.2 ns) and two bands of negative parity have been identified. The bands are discussed in terms of two-quasiparticle configurations. For the band built on the 4_? isomer the configuration πg9/2?νf5/2 or p3/2 is proposed.     

Uniaxial stress measurements on the 1039.8 meV zero-phonon line in irradiated silicon.

A vibronic band in Si with its zero-phonon line at 1039.8 meV is a product of neutron irradiation and annealing at 500 to 800 K. We show that uniaxial stresses perturb the zero-phonon line as expected for a tetragonal centre. Since the TA(X) phonons are particularly important in forming the phonon sideband, we suggest that the tetragonal symmetry is a result of a naturally axial centre, and is not a Jahn-Teller distortion of a T_d centre. No stress-induced reorientation of the centre occurs at small stress perturbations, but when the zero-phonon line splitting is comparable with the TA(X) energies the high energy stress-split component decreases rapidly in intensity. The zero-phonon line is negligibly affected by magnetic fields of up to 5 Tesla.     

Investigation of i132 excitations in 197Hg and 191Pt

The level schemes of the odd-neutron nuclei ¹⁹⁷Hg and ¹⁹¹Pt have been studied using in-beam spectroscopic methods. Energies, intensities, angular distributions and coincidences of the γ-rays following (α, 2n) reactions were measured. Also conversion electrons and delayed γ-ray spectra were recorded. Most of the levels in both nuclei are de-populated via the $\text{13}\text{2}{}^{\mathrm{+}}$ isomers. Besides the yrast states, several additional states with spin values between $\text{13}\text{2}$ and $\text{21}\text{2}$ were identified. The negative parity of a side band in ¹⁹⁷Hg starting with an $\text{f =}\text{21}\text{2}$ state was proved by the conversion electron measurement. The families of positive-parity states were compared with model calculations where the core was described as rigid triaxial rotor or anharmonic vibrator. For ¹⁹⁷Hg both models give similarly good results for the energy spectrum and the branching ratios of electromagnetic transitions. Several negative-parity states found in ¹⁹⁷Hg are compared with the predictions of a pairing-plus-quadrupole model.     

Special solutions of the equations Pu = 0, Pu = δ for invariant linear differential operators with polynomial coefficients

Explicit formulas are given for certain solutions of the equations $\text{Pu = δ}\text{and}\text{P}\text{u}\text{?}\text{= 0}$ with P being a differential operator with polynomial coefficients preserving the form ∑_{i = 1}ⁿx_i^p ? ∑_{i = 1}^my_i^q for arbitrary even integers p, q. These formulas are a direct consequence of the invariance of P and depend only up to a constant factor upon the operator P.     

Photoproduction of πmesons off protons from the Δ(1232) region to Eγ = 3 GeV

Photoproduction of π⁰-mesons was studied with the Crystal-Barrel detector at ELSA for incident energies from 300MeV to 3GeV. Differential cross-sections dσ/dΩ, dσ/dt, and the total cross-section are presented. For E _γ < 3GeV, the angular distributions agree well with the SAID parametrization. At photon energies above 1.5GeV, a strong forward peaking indicates t-channel exchange to be the dominant process. The rapid variations of the cross-section with energy and angle indicate production of resonances. An interpretation of the data within the Bonn-Gatchina partial-wave analysis is briefly discussed.     

Structural, thermal, and spectral investigations of the lanthanide(III) biphenyl-4,4′-dicarboxylates

The lanthanide biphenyl-4,4′-dicarboxylates (bpdc) series of the general formulae Ln₂(bpdc)₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III); bpdc = C₁₂H₅(COO) ₂ ^2? ; n = 4, 5 or 6 have been obtained by the conventional precipitation method. All prepared complexes were characterized by elemental analysis, simultaneous thermal analyses thermogravimetric-differential scanning calorimetry (TG–DSC) and TG–FT-IR, FT-IR, and FT-Raman spectroscopy as well as X-ray diffraction patterns measurements. In the whole series of analyzed complexes the bpdc^2? ligand is completely deprotonated. In view of that, four carboxylate oxygen atoms are engaged in the coordination of Ln(III) ions. The synthesized compounds are polycrystalline and insoluble in water. They crystallize in the low symmetry crystal systems, like monoclinic and triclinic. Heating in the air atmosphere resulted in the multi-steps decomposition process, namely endothermic dehydration and strong exothermic decomposition processes. The dehydration process leads to the formation of stable anhydrous Ln₂bpdc₃ compounds which subsequently decompose to the corresponding lanthanide oxides.     

Fast and simple method for determination of fatty acid methyl esters (FAME) in biodiesel blends using X-ray spectrometry

The determination of fatty acid methyl esters (FAME) in diesel fuel blends is an important aspect of production and blending process as well as quality control of distribution operations. In this study, energy-dispersive X-ray fluorescence spectrometer (EDXRF) is used for the first time for determination of FAME in biodiesel blends. The principle of the method is based on intensity difference of X-ray radiation scattered from hydrocarbons and from FAME. The experiment shows that coherent and incoherent radiation, commonly applied for evaluation of the average atomic number of the sample with light matrix, cannot be applied for FAME determination. However, the application of scattered continuous radiation gives excellent correlation between FAME concentration and intensity of scattered radiation. The best results are obtained if continuum is collected in the range of energy between 10.5 and 15.0 keV for rhodium X-ray tube, operated at 35 kV. Linear relationship between the FAME concentration and the inverse of scattered continuous radiation is obtained with the correlation coefficients of 0.999. Standard deviation of measurement is ca. 0.46% (v/v) of FAME and detection limit is 1.2% (v/v) for 600 s counting time and 50% dead-time loss using Si-PIN detector. The investigation shows that crucial issue in determination of FAME in biodiesel blends using EDXRF spectrometer is the precision of measurements resulting from the counting statistics. Therefore, much better results (0.20% (v/v) standard deviation and 0.52% (v/v) detection limit) can be expected if higher intensity of primary radiation is applied and X-ray spectrum is collected by silicon drift detector of high input count rate. For concentration of FAME from 10 to 100% (v/v), the differences between reference method (Fourier transform infrared spectrometry) and the proposed method usually do not exceed 1% (v/v) of FAME. The proposed method is fast, simple and enables FAME determination in wide range of concentration up to 100% of FAME without any sample treatment.     

Synthetic studies on dicyclopenta[a,d]cyclooctane terpenoids: construction of the core structure of fusicoccins and ophiobolins on the route involving a Wagner-Meerwein rearrangement

The total diastereoselective synthesis of dicyclopenta[a,d]cyclooctane core skeleton of tricyclic terpenoids, fusicoccins, and ophiobolins is reported. The synthesis commences from 2-methylcyclopent-2-en-1-one and leads first to the easily accessible intermediary cyclopenta[8]annulene 18. The subsequent steps include two key transformations: shifting the angular methyl group from the angular to the neighboring position employing a carbocationic rearrangement (26 → 28) and construction of a quaternary stereogenic center via alkylation of α-methylcyclooctanone intermediate (38 → 48). In the context of the latter transformation, a series of model experiments on alkylation of 2-methylcyclooctan-1-one were conducted. The stereochemical assignments were verified by X-ray analyses of the key structures 39 and 50.