Volume 58, Issue 12

We find new solitary-wave solutions of the higher order nonlinear Schrödinger equation with both real and imaginary Raman terms, which can model an ultrashort pulse propagation through optical fibers, under some constraint among the model coefficients. The physical conditions such as the wavelength needed to launch the pulse, the types of optical fibers, and the required peak power, are obtained from the constraints for the solitary-wave solutions. - PACS number(s): 42.65.Tg, 42.81Dp, 02.30.Jr, 42.79.Sz.

The local structure and the EPR parameters (zero-field splitting D, g factors g ‖ and g ⊥ and hyperfine structure constants A ‖ and A⊥) ofMn 4+ in LiF:U:Mn crystal have theoretically been investigated by using the perturbation formulas of the EPR parameters for a 3d 3 ion in trigonally distorted octahedra. In this trigonal Mn 4+ center, three U 6+ ions locate on (1,1,0), (1,0,1) and (0,1,1) sites, each surrounded by six O 2− ions. Thus, the studied system is characterized as the Mn 4+ associated with one host F − triangle, one O 2− triangle and an additional equivalent F’ − triangle containing the three U 6+ ions, i.e. an [MnF 3 O 3 F’ 3 ] 8 − cluster. The central Mn 4+ impurity is found to shift towards the oxygen triangle along the C 3 (or [111]) axis by an amount ΔZ (≈ 0.29 Å) due to the strong electrostatic attraction between the Mn 4+ and the oxygen triangle (and also the additional equivalent F’ − triangle), which increases the trigonal distortion of the Mn 4+ center considerably. The calculated EPR parameters based on the above displacement ΔZ agree reasonably with the observed values.

Electron spin resonance of Mn 2+ doped in Eu 2 M” 3 (NO 3 ) 12 .24H 2 O (M” = Zn, Co) single crystals has been studied at 295 and 77 K using an X-band spectrometer. The observation of resolved Mn 2+ spectra in Eu 2 Co 3 (NO 3 )12.24H 2 O at 295 K have been interpreted in terms of random modulation of interaction between Mn 2+ and divalent cobalt ions by the rapid spin-lattice relaxation of cobalt ions. T1 of divalent cobalt has been estimated to be ∼ 5×10 −12 s at 295 K. The superposition model is applied to the zero-field splitting parameter D.- PACS: 76.30 F

In the King’s Problem, a physicist is asked to prepare a d-state quantum system in any state of her choosing and give it to a king who measures one of (d+1) sets of mutually unbiased observables on it. The physicist is then allowed to make a control measurement on the system, following which the king reveals which set of observables he measured and challenges the physicist to predict correctly all the eigenvalues he found. This paper obtains an upper bound on the physicist’s probability of success at this task if she is allowed to make measurements only on the system itself (the “conventional” solution) and not on the system as well as any ancillary systems it may have been coupled to in the preparation phase, as in the perfect solutions proposed recently. An optimal conventional solution, with a success probability of 0.7, is constructed in d = 4; this is to be contrasted with the success probability of 0.902 for the optimal conventional solution in d = 2. The gap between the best conventional solution and the perfect solution grows quite rapidly with increasing d.

The changes of defect characteristics induced by accelerated lifetime tests on solar cells of the heterostructure ZnO/CdS/Cu(In,Ga)(S,Se) 2 /Mo are investigated. Encapsulated modules were shown to be stable against water vapor and oxygen under outdoor conditions, whereas the fill factor and open-circuit voltage of non-encapsulated test cells are reduced after prolonged damp heat treatment in the laboratory, leading to a reduced energy conversion efficiency. We subjected non-encapsulated test cells to extended damp heat exposure at 85 ◦C ambient temperature and 85% relative humidity for various time periods (6 h, 24 h, 144 h, 294 h, and 438 h). In order to understand the origin of the pronounced changes of the cells, we applied temperature-dependent current-voltage and capacitance voltage measurements, admittance spectroscopy, and deep-level transient spectroscopy. We observed the presence of electronic defect states which show an increasing activation energy due to damp heat exposure. The corresponding attempt-to-escape frequency and activation energy of these defect states obey the Meyer-Neldel relation. We conclude that the response originates from an energetically continuous distribution of defect states in the vicinity of the CdS/chalcopyrite interface. The increase in activation energy indicates a reduced band bending at the Cu(In,Ga)(S,Se) 2 surface.We also observed changes in the bulk defect spectra due to the damp-heat treatment. - PACS: 73.20.hb, 73.61.Le

We study the stationary shapes and the rotational motion of drops of magnetic fluids floating in a non-magnetic liquid of equal density and spun up by an externally applied rotating magnetic field. For a sufficiently large magnetic susceptibility of the drop fluid transitions to non axial-symmetric shapes take place when the field amplitude is increased. We give a detailed theoretical account of the character of these shape bifurcations, of the resulting stationary drop forms, and of the slow rotational motion of the drop and compare our findings with results obtained in an experimental realization of the system. Quantitative agreement between theory and experiment can be obtained when saturation effects in the magnetization curve of the ferrofluid are taken into account. PACS numbers: 47.20.Hw, 47.55.Dz, 75.50.Mm

Crystals of [(CH 2 OH) 3 CNH 3 ]H 2 AsO 4 have been grown, and X-ray diffraction analysis has shown them to be monoclinic, with space group P2 1 . A three-dimensional network of hydrogen bonds of the type O-H. . . O and N-H. . . O forms strong cation-cation and cation-anion linkages. Stabilizing the structure, they create favourable conditions in the crystal to be polar. The temperature dependent behaviour of the dielectric permittivity, measured along three crystal axes in the range 100 - 300 K, did not show any evidence for a phase transition, while the pyroelectric properties of the crystal confirmed the lack of a centre of symmetry. These polar features locate [(CH 2 OH) 3 CNH 3 ]H 2 AsO 4 among the materials applicable to electrooptics and for the second harmonic generation.

The pressure dependence of the 129 Xe chemical shift tensor confined in the Tris(o-phenylenedioxy) cyclotriphosphazene (TPP) nanochannel was investigated by high-pressure 129 Xe NMR spectroscopy. The observed 129Xe spectrum in the one-dimensional TPP nanochannel (0.45 nm in diameter) exhibits a powder pattern broadened by an axially symmetric chemical shift tensor. As the pressure increases from 0.02 to 7.0 MPa, a deshielding of 90 ppm is observed for the perpendicular component of the chemical shift tensor δ ⊥ , whereas a deshielding of about 30 ppm is observed for the parallel one, δ ‖ . This suggests that the components of the chemical shift tensor, δ ‖ and δ ⊥ , are mainly dominated by the Xe-wall and Xe-Xe interaction, respectively. Furthermore, the effect of helium, which is present along with xenon gas, on the 129 Xe chemical shift is examined in detail. The average distance between the Xe atoms in the nanochannel is estimated to be 0.54 nm. This was found by using δ ⊥ at the saturated pressure of xenon, and comparing the increment of the chemical shift value in δ ⊥ to that of a β -phenol/Xe compound.

Synthesis and Characterization of N (p-n-alkyl benzylidene)-p-n-alkoxy anilines (n.Om), N (p-nalkoxy benzylidene)-p-n-alkoxy anilines (nO.Om) and N (p-n-alkyl benzylidene)-p-n-alkyl anilines (n.m), where n = m = either 4 or 5, has been carried out using thermal microscopy (TM) and differential scanning calorimetry (DSC). The results are discussed in the light of other experimental observations on N (p-n-alkoxy benzylidene)-p-n alkyl anilines (nO.m). It has been observed that the position of oxygen on either side of the rigid core of the benzylidene moiety plays an important role in the manifestation of different phase variants.

MINDO-Forces calculations with complete geometry optimization have been performed on cyclopentanone and its enol counter part, perfluorination of cyclop entanone and its enol counterpart and X-cyclopentanones and their X-enols, where X is NO 2 , CF 3 , CN, OH, NH 2 and O − . It was found that ketone is more stable than its enol counterpart. Perfluorination destabilizes ketone on the expense of enol. These results agree with the experimental results and density functional theory calculations. All substituents are destabilizing except O− in the case of cyclopentanone. It was found that NO 2 and CF 3 behave as strong electron withdrawing groups, CN and NC show amphielectronic behavior, and the substituents OH,NH 2 and O − behave as electron releasing groups with O − being strongest. Geometrical parameters, heats of formation, entropies, and Gibbs free energies are reported

MINDO-Forces calculations have been performed with complete optimization of the geometries on stepwise fluorinated cyclopropanones and their enols. Increase in the number of fluorine atoms causes destabilization of cyclopropanone. Perfluorinated enol was found to be present in substantial concentration, as was mentioned in previous work. This is supported by calculations of Gibbs free energies and isodesmic reactions. Geometrical parameters, heats of formation, electron densities, dipole moments and orbital energies (HOMO-LUMO) are reported.

Rüdenberg’s well-known letter of 1951 entitled “On the Three- and Four-Center Integrals in Molecular Quantum Mechanics” explicitly presents two approximation formulas for four-center repulsion integrals, only. When applied to some types of three-center repulsion integrals, however, these two recipes still imply considerable oversimplifications. Using both one-electron and two-electron routes of Rüdenberg’s truncated expansion, on the other hand, such shortcomings can be avoided strictly. Starting from four simple “Unrestricted and Combined” (U&C) approximation schemes introduced elsewhere, an improved “Restricted and Combined” (R&C) approximation picture for Fock-matrix elements now will be outlined, which does not tolerate any unnecessary oversimplifications. Although the simplicity of the U&C scheme is lost in this case, R&C-approximated Fock-matrix elements still can be constructed from one- and two-center integrals alone in an effective way. Moreover, due to their dependence on a single geometric parameter, all types of two-center integrals can be calculated in advance for about one hundred fixed interatomic distances at the desired level of sophistication and stored once and for all. A cubic spline algorithm may be taken to interpolate the actual integral value from each precomputed list.

The analysis based on Rüdenberg’s well-known letter of 1951, which has been outlined for molecules in a preceding contribution, now will be transfered to translational periodic systems in one, two, or three dimensions. Again, when applied unrestrictedly to “Linear Combination of Atomic Orbitals” representations (LCAO) of both “Unrestricted” and “Restricted Hartree-Fock” pictures (UHF and RHF), Rüdenberg’s integral approximations of Mulliken type lead to a thorough interpretation of “Extended Hückel” crystal orbital theories (EHT). Moreover, Rüdenberg’s ideas provide us with “Unrestricted and Combined” extensions (U&C) of the widely-used approximation schemes “Zero Differential Overlap” (ZDO) and “Neglect of Diatomic Differential Overlap” (NDDO). An improved variant of EHT is also presented. Corresponding “Restricted and Combined” concepts (R&C), which overcome some shortcomings inherent in Rüdenberg’s original recipes, will be sketched.

35 N-(Phenyl)-, N-(2/4-chlorophenyl)- and N-(2/4-methylphenyl)-substituted acetamides are prepared, characterised and their NMR spectra studied in solution state. The variation of the chemical shifts of the aromatic protons in these compounds follow more or less the same trend with changes in the side chain. The chemical shifts remain almost the same on introduction of Cl substituent to the benzene ring, while that of methyl group lowers the chemical shifts of the aromatic protons. But only 13 C-1 and 13 C-4 chemical shifts in these compounds are sensitive to variations of the side chain. The incremental shifts in the chemical shifts of the aromatic protons and carbons due to -COCH 3−i X i or NHCOCH 3−i X i groups in all the N-(phenyl)-substituted acetamides, C 6 H 5 NHCOCH 3−i X i (where X = Cl or CH 3 and i = 0, 1, 2 or 3) are calculated. These incremental chemical shifts are used to calculate the chemical shifts of the aromatic protons and carbons in all the N-(2/4-chlorophenyl)- and N-(2/4-methylphenyl)-substituted acetamides, in two ways. In the first way, the chemical shifts of aromatic protons or carbons are computed by adding the incremental shifts due to -COCH 3−i X i groups and the substituents at the 2 nd or 4 th position in the benzene ring to the chemical shifts of the corresponding aromatic protons or carbons of the parent aniline. In the second way, the chemical shifts are calculated by adding the incremental shifts due to -NHCOCH 3−i X i groups and the substituents at the 2 nd or 4 th position in the benzene ring to the chemical shift of a benzene proton or carbon, respectively. Comparison of the two sets of calculated chemical shifts of the aromatic protons or carbons of all the compounds revealed that the two procedures of calculation lead to almost the same values in most cases and agree well with the experimental chemical shifts.

A new class of dissipative structures is proposed that live in real space rather than phase space. A light ray passing through a soup of randomly moving gravitating masses is a case in point. It suffers a “dynamic path elongation” since the random pushes and pulls have a greater probability of increasing than decreasing its path length. Time reversal then re-shrinks the path in question in a conspirational manner, while a close-by nonselected path gets expanded. This is a new statistical-mechanics phenomenon. The latter at the same time qualitatively reproduces the well-known Hubble phenomenon of distance-proportional light-path expansion in the cosmos. A preliminary quantitative estimate, based on the Birkinshaw equation with an assumed bias factor of three, is also presented.