Shape coexistence in light se isotopes: evidence for oblate shapes

Lifetimes of states in the ground-state bands of (70)Se and (72)Se were measured using the recoil-distance Doppler shift method. The results deviate significantly from earlier measurements, requiring a revision of the conclusions drawn from a recent Coulomb excitation experiment concerning the shape of (70)Se. The new results lead to a coherent picture of shape coexistence in the neutron-deficient selenium and krypton isotopes. The coexistence and evolution of oblate and prolate shapes in this mass region is for the first time consistently described by new Hartree-Fock-Bogolyubov-based configuration-mixing calculations which were performed using the Gogny D1S interaction.     

Particle-triaxial rotor calculations for the low-lying states with negative parity in 193Os

It is shown that the particle-triaxial rotor model is able to describe the low-lying levels with negative parity in ¹⁹³Os supporting their doublet structure. At low excitation energy, the model calculations can be used for a clarification of the spin assignments in cases where they are ambiguous. It is of great interest to check the predictions of the model experimentally by new precise spin determination.     

Optodynamic monitoring of laser micro-drilling of glass by using a laser probe

We present a new method for monitoring of the laser micro-drilling process. The method is based on detection of acoustic waves in air above the processed sample using a laser beam deflection probe (LBDP). We present an augmentation of the experimental set-up by means of a digital micrographic system which enables the acquisition of images of the plasma plume and of the hole cross-section during a drilling sequence. Comparing the acquired images with the detected LBDP signals, we examine the drilling process from a new perspective.     

Synthesis of linear systems with desired equivalent form

A method for feedback synthesis of linear control systems with desired linearly equivalent form of the closed loop system matrix is proposed. The method is based on the serial canonical form of linear multivariable systems which is an alternative to the Luenberger canonical form. A stable computational algorithm for finding the serial canonical form using orthogonal similarity transformations is described. The algorithm for synthesis involves a simple recurrent procedure and gives the possibility to achieve any attainable equivalent form of the closed loop system. The results obtained are extended to the synthesis of reduced order state observers.     

Infrared Absorption Studies of Some New 1,8-Naphthalimides

Some new 4-nitro- and 4-allylamino-N-phenyl-1,8-naphthalimides comprising different substituents in the phenyl ring have been studied by infrared absorption spectroscopy. The effect of the nature of the substituents upon the vibration frequencies of the carbonyl groups has been discussed.     

Experimental and theoretical spectral properties of ethyl 2-(7-hydroxy-2-oxo-2H-chromen-4-yl)acetate doped sol-gel materials: new materials with potential optical application

Silica xerogels and monoliths, containing ethyl 2-(7-hydroxy-2-oxo-2H-chromen-4-yl)acetate (K4) or Sm^{3 +} ions and K4 are prepared by sol-gel technique. NMR investigations, UV/Vis, IR- and luminescence spectral properties of K4 in solution and in monoliths are presented. The IR-spectroscopic properties of the prepared sol-gel materials are examined by applying the reduced-difference procedure to non-polarized IR-spectra. The results show that the sol-gel medium did not interact with K4 as well as in the presence of Sm³⁺ ions the K4 form a [Sm(L)₂(H₂O)₄] × (NO₃)₃ complex in the matrix. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mercury binding sites in thiol-functionalized mesostructured silica

Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO(2))(1)(-)(x)()(LSiO(1.5))(x)(), where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S < or = 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBu(t))(2). At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands.     

Studies on the uncertainties in quantitative EPR estimations due to the construction of the cavities used

The magnitude of the continuous wave electron paramagnetic resonance (CW-EPR) response of a given sample is governed by several cavity parameters. Two of them are the distribution of the modulation magnetic flux density and the microwave magnetic component over the sample length. Their mutual configuration could have a significant influence on quantitative EPR estimations. In the present paper, we report the results obtained with 14 different cavities of TE₁₀₂, TE₁₀₄, TM₁₁₀ and TM₀₁₁ modes commercially available and used in many EPR laboratories with respect to the magnitude of their EPR response as a function of the sample length. The results show that due to their technical construction the widely used cavities in CW-EPR spectroscopy could be classified into three types in which: (i) the distribution of the microwave magnetic component in the cavity coincides with the modulation magnetic flux; (ii) the modulation magnetic flux is wider than the microwave magnetic component in the cavity. In this type, the magnitude of the EPR response along the sample length is governed only by the distribution of the microwave magnetic component in the cavity, (iii) the modulation magnetic flux is narrower than to the microwave magnetic component in the cavity. In the cavities of this type, the magnitude of the EPR response is governed by the distribution of the modulation magnetic flux. Whereas, in both former types, the EPR response corresponds to the full length of the sample along the z-axis of the cavity, an EPR silent zone appears in the latter type. In some of them this zone takes ca. 40% of their full length. Therefore, the assumption that the EPR active zone corresponds to the full cavity length (along the sample axis) is not valid for the latter type cavities. Their use will give 2-3% error within a series of samples, but the results will be burdened by a systematic error and could not be compared with the data obtained with another cavity even on the same spectrometer. In view of this, we should be familiar with the features of every cavity before using it for quantitative EPR estimations. Two ways are recommended to overcome the effect of EPR silent zones of an unknown cavity in order to get comparable results in quantitative EPR estimations: (i) to use samples of less than 5-6 mm length, symmetrically situated with respect to the cavity center in consecutive procedures of estimations independently of the cavity type, (ii) in the cases of simultaneous recording of unknown sample and a standard they both should be homogeneously mixed or coaxially situated along their full length.     

Tautomerism of rhodanine

Semiempirical (MINDO/3, AM1, PM3, MNDO) and ab initio (4-31G and 4-3IG + dAO/S basis sets) calculations on the relative stabilities and structures of the five potential tautomeric forms of rhodanine are reported. It is shown that all methods (excepting PM3) predict as most stable 2-thioxo-4-thiazolidinone. These results correspond to the known experimental data. The infrared spectrum of rhodanine was recorded for the region 4000-150 cm^–1, and the characteristic bands were compared with AM1 and 4-31G + dAO/S calculated frequencies. The transition states between five pairs of all possible tautomeric forms of the rhodanine were found by the AM1 method.     

Photochemical dehydrogenation of 3-acetyl-3,4-dihydrocoumarin

Summary The ultraviolet irradiation of air-saturated alcoholic solutions of 3-acetyl-3,4-dihydrocoumarin (1) leads to the formation of 3-acetylcoumarin (2) and 3,3-diacetyl-3,3,4,4-tetrahydro-4,4-biscoumarin (3). The presence of molecular oxygen is an indispensable condition for the occurrence of a photodehydrogenation process, which is quantitatively when effected on silica gel.

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Photochemische Dehydrierung von 3-Acetyl-3,4-dihydrocumarin (Kurze Mitt.)

Zusammenfassung Bei UV-Bestrahlung von alkoholischen Lösungen von 3-Acetyl-3,4-dihydrocumarin (1) unter O₂ werden 3-Acetylcumarin (2) und 3,3-Diacetyl-3,3,4,4-biscumarin (3) gebildet. Die Anwesenheit von molekularem O₂ ist für die Photodehydrierung erforderlich, wobei die Umsetzung an Silikagel quantitativ verläuft.