Hierarchy of critical exponents of currents on -simplex fractals

Using the symmetry of ( d +1)-simplex fractals with decimation number b =2, the current distribution has been determined. Then using the renormalization group technique, based on the independent Schur's invariant polynomials of current distributions, the multifractal spectrum of even moments of current distributions has been evaluated analytically up to order six for an arbitrary value of d. Also the scaling exponents of order 8 and order 10 have been calculated numerically up to d =30. Received: 19 November 1997 / Revised: 21 January 1998 / Accepted: 9 February 1998     

Reanalysis and semi-empirical predictions of the hyperfine structure of in the model space

On the basis of most of the earlier hyperfine-structure (hfs) experimental results, the hfs of the atomic zirconium has been reanalyzed by the simultaneous parameterization of the one- and two-body interactions for the model space (4 d + 5 s ) ⁴ . The values of the one- and two-body hfs parameters have been determined and the nuclear quadrupole moment, free of Sternheimer corrections up to second order, has been evaluated. Moreover, the values of the magnetic-dipole A and the electric-quadrupole B constants for all known levels of this model space have been predicted. Received: 22 December 1997 / Revised: 15 May 1998 / Accepted: 1 July 1998     

Lifetime measurements for some levels in Be-like Cl XIV and S XIII

Lifetime measurements have been carried out for some low lying (n = 2) levels in the four-electron ions Cl XIV and S XIII using the beam-foil technique. Accurate oscillator strengths for the 2 s2 ¹ S - 2 s 2 p ¹ P o transition have been determined by the inclusion of prominent cascades in the analysis. Lifetimes of the levels of the 2 p2 ³ P j multiplet have also been measured for both ions. The results are compared with theoretical predictions and earlier measurements. Received: 29 October 1997 / Revised: 10 February 1998 / Accepted: 5 March 1998     

Ultraviolet photoelectron spectroscopy of Si 4 - to Si 1000 -

Using a new experimental setup we have measured UV (h ν = 6.4 eV) photoelectron spectra of cold silicon cluster anions Si _n ^- in a very broad size range. For sizes up to n = 46 the spectra exhibit rich structures. For larger sizes only smooth spectra have been obtained. No trace of a bandgap has been found even for clusters with more than 1000 atoms. Received 30 November 2000     

Structural investigation of a new variety of the low dimensional conductor with 2 m = 5 + 5: P 4 W 10 O 38

A new variety of P ₄ W ₁₀ O ₃₈ , m = 5 member of the monophosphate tungsten-bronze family with pentagonal tunnels (MPTB p), , has been isolated and studied by X-ray diffraction measurements. The structure has been solved by direct methods from single crystal X-ray data. The monoclinic unit cell corresponds to a regular stacking of WO ₃ -type slabs which are all five-WO ₆ -octahedra thick and connected through PO ₄ tetrahedra. This structure is comparable to that previously described for the MPTB p'series with m = 4 (P ₄ W ₈ O ₃₂ ) and m = 6 (P ₄ W ₁₂ O ₄₄ ). An X-ray diffuse scattering investigation has revealed that this member is subjected to charge density wave instabilities (CDW) located on chains running along the directions. Two CDW transitions have been observed at and , bearing some resemblance with those exhibited by the m = 4 member. The corresponding modulation wave vectors can be accounted for by a hidden nesting mechanism which connects the crossing points of differently oriented quasi-planar Fermi surfaces, as found for the low m (4 and 6) members of the MPTB's. Received 12 March 1999 and received in final form 20 May 1999     

High resolution laser spectroscopy of NaAr: Improved interaction potential for the ground state

The absorption spectrum of NaAr has been investigated with high resolution using a supersonic beam of molecules and a tunable dye laser. About 3 300 absorption lines due to the transition A ² Π ← X and B ² Σ ← X have been observed. In addition, we observed the spectral distribution of the fluorescence for a particular absorption line. From all experimental data the X ² Σ ⁺ interaction potential has been deduced in a fully quantum-mechanical method of approach. The potential is given in terms of an analytical Hartree-Fock-Dispersion function. For the equilibrium parameters of the X state we get R _e = 5.01(1) ? and D _e = 41.6(2) cm ^-1 . Received 28 August 2002 / Received in final form 15 October 2002 Published online 17 December 2002 RID="a" ID="a"Now at Knick Elektronische Messger?te, Beuckestr. 22, 14163 Berlin, Germany. RID="b" ID="b"e-mail: dz@kalium.physik.tu-berlin.de     

Hyperfine structure and isotope shift measurements on 4d10 1S0 → 4d9 5p J=1 transitions in Pd I using deep-UV cw laser spectroscopy

The 4 d ^{10 1} S₀ ground-state transitions to the 4 d ⁹ 5 p configuration of palladium (Pd) have been studied. For this purpose, a tunable, single-mode, deep-UV cw laser has been built to generate the sum frequency of a frequency-doubled Ti:S laser with a second Ti:S laser. The produced wavelengths range from 244 to 276 nm. From the measured spectra the frequency splitting due to hyperfine structure and isotope shift, the hyperfine structure A and B constants and the lifetimes of the states have been extracted. Received 3 October 2001     

Molecular alignment of biphenyl derivatives -a computational analysis

Molecular alignment of some biphenyl derivatives likes 4'-Nitro-2-biphenylamine (NBPA), 4-Acetyl-3'-chlorobiphenyl (ACBP) and 4-Acetyl-3'-florobiphenyl (AFBP) has been examined. The CNDO/2 method has been employed to compute the net atomic charge and atomic dipole-moment components at each atomic centre. Configurational energy has been computed using a modified Rayleigh- Schrodinger perturbation method at an interval of 0.1 A° in translation and 1° in rotation, and corresponding probabilities have been calculated using MB-statistics. A comparative study of molecular parameters like the total energy, the binding energy and the total dipole moment etc., has been made. On the basis of the stacking and the in-plane interaction energy calculations, all the possible geometrical arrangements between molecular pairing have been obtained. The investigation suggests that a strong intermolecular interaction energy between a pair of NBPA molecules, and the specific minimum energy configuration, determines the alignment of molecules with respect to one another. An attempt has been made to correlate the liquid crystalline properties exhibited by this class of molecules, and thereby develop a molecular model for the liquid crystallinity.     

Theoretical study of molecular ordering in liquid crystals with the help of intermolecular interaction energy calculations

A theoretical analysis has been carried out to determine the molecular alignment of some nematic liquid crystals like DPAB (4, 4'-di-n-propoxy-azoxybenzene), EPAB (ethyl para-azoxybenzoate) and PAA (para-azoxyanisole). CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecules. Configurational energy has been computed using a modified Rayleigh-Schrodinger perturbation method at an interval of 1 Å in translation and 10° in rotation between a pair of DPAB molecules. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible geometrical arrangements between a molecular pair have been considered. A comparative picture of molecular parameters like total energy, binding energy, total dipole moment etc., has been obtained. An attempt has been made to explain the nematogenic behaviour of liquid crystal and thereby develop a molecular model for liquid crystallinity.     

1H and 13C NMR Spectral Study of Some 2r-Aryl-6c-phenylthian-4-ones,Their 1-Oxides and 1,1-Dioxides

ABSTRACT

Four 2r-aryl-6c-phenylthian-4-ones 1b?1e and their 1-oxides 2b?2e and 1,1-dioxides 3b?3e have been newly synthesized. ¹H and ¹³C NMR spectra have been recorded for all these compounds and 2r,6c-diphenylthian-4-one 1-oxide 2a. ¹³C NMR spectrum has been recorded for the sulfone 3a of 1a. For selected compounds ¹H-¹H COSY, HSQC, HMBC, and NOESY spectra have been recorded. The vicinal proton–proton coupling constants suggest that in all these compounds, the heterocyclic ring adopts chair conformation with equatorial orientations of the aryl and phenyl groups. Proton and carbon chemical shifts suggest that in the sulfoxides, the S=O bond is axial and enhances the J _aa value by some special effect. The S = O bond causes a significant upfield shift even on carbons without hydrogens. Significant solvent shifts also were observed.     

Brillouin scattering study of transverse elastic waves in the α, incommensurate and β phases of AlPO4

Transverse and pseudo-transverse elastic waves have been studied in several scattering geometries in order to investigate the temperature dependences of C E ₆₆ and C E ₁₄ over the range 300-1100 K, including the transitions near 860 K. These results complete those on C E ₄₄ we have obtained in a previous work. All these constants display discontinuities at the lock-in transition. In the phase, the results are analysed in term of lowest order couplings between strains (e) and the order parameter (Q). The main features are described by the lowest order biquadratic e2Q2 coupling, in particular for C E ₄₄ in a large temperature range. However, it appears that a contribution of the next coupling term arises for C E ₆₆ below K and that the first two lowest order terms have to be taken into account even just below the lock-in transition in the case of C E ₁₄ . The temperature dependence of Q has been deduced and it can be well described in the framework of Landau's theory. Received: 2 October 1997 / Received in final form: 3 December 1997 / Accepted: 29 January 1998     

Investigations on the soft-mode mechanism of the ferroelectric phase transition in

Dielectric and Raman spectroscopic measurements have been performed to investigate the ferroelectric phase transition in . Single crystals were grown by the zone melting method. The frequency dependence of the dielectric permittivity from 1 MHz to 1 GHz has been studied in a temperature range between 265 and 285 K. A Debye like dielectric dispersion was found, showing a critical slowing down around K. Polarized Raman spectra have been taken between 220 and 310 K. Two softening modes have been found, one of A- and another one of B / B g-symmetry. The phase transition mechanism in can be classified as partially order-disorder and partially displacive, confirming former structural results. It resembles strongly that of monoclinic . Received: 7 April 1998 / Revised: 5 June 1998 / Accepted: 16 June 1998     

Isotope shifts and hyperfine structure in the transitions of gadolinium

High-resolution resonance ionization mass spectrometry has been used to measure isotope shifts and hyperfine structure in all (J = 2-6) and the transitions of gadolinium (Gd I). Gadolinium atoms in an atomic beam were excited with a tunable single-frequency laser in the wavelength range of 422-429 nm. Resonant excitation was followed by photoionization with the 363.8 nm line of an argon ion laser and resulting ions were mass separated and detected with a quadrupole mass spectrometer. Isotope shifts for all stable gadolinium isotopes in these transitions have been measured for the first time. Additionally, the hyperfine structure constants of the upper states have been derived for the isotopes ^{155, 157} Gd and are compared with previous work. Using prior experimental values for the mean nuclear charge radii, derived from the combination of muonic atoms and electron scattering data, field shift and specific mass shift coefficients for the investigated transitions have been determined and nuclear charge parameters for the minor isotopes ^{152, 154} Gd have been calculated. Received 18 November 1999     

Diode laser slit-jet spectra and analysis of the fundamental of 1-chloro-1,1-difluoroethane (HCFC-142b)

High resolution infrared spectra (0.001 cm^-1) have been measured for mixtures of 1-chloro-1,1-difluoroethane in Ne, expanded in a supersonic planar jet. The ν ₇ fundamental has been analyzed for both isotopic species, CH₃CF₂ ³⁵Cl and CH₃CF₂ ³⁷Cl. A weak b-type component has been observed for the first time. Received 20 May 2002 / Received in final form 10 July 2002 Published online 24 September 2002 RID="a" ID="a"Also: Dipartimento di Scienze Fisiche Universitá di Napoli “Federico II” Complesso Universitario di M.S. Angelo, 80126 Napoli, Italy. e-mail: m.snels@isac.cnr.it     

Synthesis and Fluorescence Studies of Some New Fluorophores and Their Effect on Hybridization of Oligodeoxyribonucleotides

Some novel fluorophores, viz. 6-(6-isobutyrylamino-1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (1), 6-(6-dimethylamino-1,3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (2), 6-(6-benzoylamino-1, 3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (3), 6-(6-amino-1-oxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (4) and 6-(6-amino-1H,3H-benzo[de] isoquinolin-2-yl)-hexanoic acid (5) have been designed, synthesized and characterized. Their comparative fluorescence has been studied in different organic solvents and aqueous solutions containing inorganic ions. Out of these, two fluorophores, 1 and 2 have been used for labelling of nucleosides which were finally converted into their phosphoramidites, and used for labelling of oligodeoxyribonucleotides through covalent attachment. These fluorophores after attachment on oligodeoxyribonucleotides showed good fluorescence signals and higher hybridisation affinity than unlabelled oligodeoxyribonucleotides.     

Structural Assignment of Isomeric S‐ and S,N‐1‐Alkoxycarbonylalkylated 6‐Amino‐2‐thiouracil Derivatives by Means of 1H and 13C NMR Spectroscopy

Abstract

The structures of new isomeric 2‐alkoxycarbonylalkylthio‐ and 2‐alkoxy‐ carbonylalkylthio‐1‐alkoxycarbonylalkyl‐6‐aminouracils (1–21) have been established on the basis of the ¹H NMR and ¹³C NMR spectroscopic data. The ¹H NMR and ¹³C NMR spectra of 1–21 have been fully assigned by a combination of two‐dimensional experiments [heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond correlation (HMBC)]. The ¹³C NMR spectra have been shown to be able to differentiate between isomers.     

Isotope shift studies in the first spectrum of dysprosium: confirmation of assignments to and new assignments to configuration

Isotope shifts (-) are reported for 221 spectral lines of the neutral dysprosium atom (Dy I) in the region 470-565 nm using a photoelectric recording Fabry-Perot spectrometer and highly enriched isotopic samples of and excited in liquid-nitrogen-cooled hollow-cathode lamps. Isotope shift data for 173 of these lines are being reported for the first time. Using the isotope shift data, term isotope shifts (-) have been evaluated for 99 even- and 68 odd-parity energy levels of Dy I. New values have been obtained for 24 odd and 36 even levels. These new values have enabled us to check some of the existing tentative assignments and also to suggest configuration assignments to a few unassigned energy levels. The earlier tentative assignments of 4 f10 5 d 6 p configuration to many high odd levels lying above have been presently confirmed. We could assign the 4f^95d6s6p configuration to 24 unassigned even levels. Received: 3 August 1998     

Stability and fragmentation of multiply ionized clusters

The stability of neutral, singly and multiply ionized silicon clusters, (N = 2-7, M = 0, , , ), has been investigated using an ab initio density functional method. We show that the fragmentation effect significantly affects the structure of mass-spectra of multiply ionized silicon clusters. For clusters, the clusters with a large fragmentation energy are found to correspond to the high peaks at N = 4 and 6 in mass-spectra. For clusters, a peak at N = 5 in mass-spectra has been predicted to be especially high. Received: 9 June 1997 / Revised: 8 January 1998 / Accepted: 25 February 1998     

Predictions of geometrical structures and ionization potentials for small barium clusters Ba

The geometrical structure of ground state Ba_n clusters (n =2-14) has been predicted from various types of calculations including two ab initio approaches used for the smaller sizes namely HF+MP2( n =2-6), DFT (LSDA)( n =2-6, 9) and one model approach HF+pairwise dispersion used for all sizes investigated here. The lowest energy configurations as well as some isomers have been investigated. The sizes n =4, 7 and 13 are predicted to be the relatively more stable ones and they correspond to the three compact structures: the tetrahedron, the pentagonal bipyramid and the icosahedron. The growth behavior from Ba₇ to Ba₁₃ appears to be characterized by the addition of atoms around a pentagonal bipyramid leading to the icosahedral structure of Ba₁₃ which is consistent with the observed size-distribution of barium clusters. Values for vertical ionization potentials calculated for n =2-5 at the CI level are seen to be in quite good agreement with recent measures. Received: 14 May 1997 / Received in final form: 2 February 1998 / Accepted: 27 February 1998     

Complete Analysis of the 1H and 13C NMR Spectra of 5-Isopropylsulfonyl-2-Norbornenes Through the Application of Two-Dimensional NMR Techniques

Total assignment of ¹³C and ¹H NMR spectra of the 5-isopropylsulfonyl-2-norbornenes 2 was achieved using the concerted application of two-dimensional homonuclear and heteronuclear chemical shift correlations. The stereochemistry of both the diastereoisomers endo 2a and exo 2b have been established using the magnitude of the proton coupling constants.