An integrated organic photoconductive detector for optoelectronics

In the system (poly-(N-vinyl carbazole) (PVK): trinitrofluorenone (TNF) a photoconductive complex is formed. Thin metal films are sputtered on BK7 glass substrates, forming two electrodes with 1 mm separation. The photoconductive complex is deposited from a solution in chlorobenzene/tetrahydrofurane on the glass substrate between the electrodes, forming a photoconductive detector. Photoconductivity of these planar detectors is studied using He-Ne laser light (=633 nm) as a function of electric field and for different TNF concentrations. An increase of photosensitivity is found for high TNF concentrations.Time resolution of the photoconductive PVK:TNF detector is investigated using a ruby pulse laser (=694 nm). The possible use of such detectors in combination with other polymer lightguides is demonstrated. Compared to most polymer waveguide materials PVK exhibits a rather high refractive index ofn=1.7. Thus the coupling of light into the photoconductive film is achieved directly. The planar structure allows further integration of polymeric components for optoelectronics.     

Classical Heisenberg antiferromagnets with nearest and next-nearest neighbor interactions on the face-centered cubic lattice: a model for EuTe?

Magnetic properties of the Heisenberg antiferromagnet with spin quantum numberS on the face-centered cubic lattice are studied as function of temperature and magnetic field, using molecular field approximation and Monte Carlo methods. In order to model Europiumtelluride, we use isotropic exchange interactions between nearest- and nextnearest neighbors; the values of these exchange constants are taken from experiments. In addition, a pseudo-dipolar anisotropy (truncated after the next-nearest neighbor distance) is included; the molecular field calculations also are performed with the full dipolar of real EuTe in two respects: the structure in zero magnetic field involves 8 sublattices in the model rather than only two; the bicritical point, above which in the temperatureT magnetic fieldH plane the spin flop phase appears, occurs atH=0 in the model rather than at nonzero field. Possible additional interactions responsible for these discrepancies are discussed. Applying finite size scaling techniques we give also a preliminary analysis of the critical behavior of the model.     

Positron-electron annihilation in the field of a fixed electric dipole

Positron annihilation from a dipole Ps state caused by simultaneous localization of the positron and electron in the field of a fixed electrical dipole is considered. The angular correlation curve of annihilation -quanta is calculated. For a fixed value of dipole moment the half width of the correlation curve decreases with decrease in dipole charge. With increase in dipole moment the correlation curve narrows. In a number of cases the given annihilation mechanism may be responsible for the appearance of the characteristic narrow component in the angular correlation spectrum. This component is usually ascribed to decay of a positronium atom. It is stressed that in interpreting the narrow component one must be careful in choosing the corresponding annihilation mechanism. Experimental results are analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 74–78, August, 1989.     

Measurement of the photoneutron flux density distribution from cylindrical targets

Measurements are performed of the density of photoneutron fluxes from cylindrical targets of²H₂O (diameter 64 and height 86 mm), Be (outer diameter 70, inner diameter 40, height 100mm), and²³⁸U (diameter 44.5 mm, height 50 mm) under the action of braking radiation from electrons with energies of 4 to 8 MeV in order to determine the effect of target form and orientation relative to the detector upon the recorded photoneutron level. The fluxes were measured by an all-wave neutron detector based on an SNM-11 counter in a paraffin retarder at an angle of 90 to the axis of the braking radiation beam for various target orientations relative to the detector. Measurement results are compared to calculations. Photoneutron fluxes from heavy water and beryllium targets of the indicated dimensions were also measured for angles of 90, 135, and 167. An isotropic nature was noted in the photoneutron fluxes from both targets.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 5–9, September, 1989.In conclusion, the authors express their gratitude to V. I. Lunev and B. M. Yakovlev for their assistance in performing the measurements.     

Theory of the singular quantum oscillator

We propose a number of arguments in favor of reevaluating the theory of a quantum oscillator described by the Hamiltonian H=–d²/dx² + 2²x² + x^–2(=2m=1). We propose that functions ₊(x) which continuously reduce to even harmonic oscillator solutions in the 0 limit be taken as the even solutions of the Hamiltonian in the –1/4 < < 3/4 range. In this scheme the problem becomes truly one-dimensional such that even and odd parity energy levels alternate, whereas the usual approach leads to parity degeneracy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 85–89, October, 1989.     

Determination of mercury in sludge and materials used for HG-eliminations from industrial waste waters by zeeman atomic absorption spectrometry after matrix modification with potassium bromide and bromine

Summary Mercury was determined by Zeeman Atomic Absorption Spectrometry after matrix modification of urine and waste water by addition of 0.1M HNO₃, 0.05M KBr, and 5l Br₂/ml, and after its extraction from sludge, iron sludge and ion exchanger by a mixture containing the same additives. The same samples were also analysed by the cold vapour method after wet oxidation of the samples in closed teflon bombs. The ratio of the corresponding concentrations was 1.21±0.39 (SD) and the concentration range covered 0.1–50000 mg Hg/kg. The analytical powers of both procedures are compared.

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Bestimmung von Quecksilber in Schlamm und in für die Reinigung industrieller Abwässer verwendeten Materialien mit der Zeeman-Atomab-sorptions-Spektrometrie nach Matrixmodifizierung durch Kaliumbromid und Brom

Zusammenfassung Quecksilber wurde mit der Zeeman-Atomabsorptions-Spektroskopie in Urin und Abwässern nach einer Matrixmodifizierung durch Zugabe von 0,1M HNO₃, 0,05M KBr und 5 l Br₂/ml sowie nach seiner Extraktion aus Schlamm, Eisenschlamm und Ionenaustauschern mit einer Mischung der gleichen Zusatzstoffe bestimmt. Die gleichen Proben wurden auch nach der Kalt-Dampf-Methode nach dem Naßaufschluß in geschlossenen Teflonbomben analysiert. Das Verhältnis der betreffenden Konzentrationen betrug 1,21±0,39 (Standardabweichung), wobei der Konzentrationsbereich 0,1–50000 mg Hg/kg umfaßte. Die analytischen Leistungsfähigkeiten der beiden Verfahren wurden verglichen.

     

The electrocapillarity of polyacrylates

Summary The electrocapillary properties of polyacrylic acid have been studied by two methods. Exploratory measurements have been made of the effect of the polymer on the differential capacity of a mercury drop in 0.1 m sodium perchlorate. They showed that the polymer was strongly adsorbed over a wide range of potentials but that it did not appear to form a monolayer. The surface excess of polymer obtained from drop weight data showed a maximum at very low concentrations and then a decline at higher concentrations. The bulk of the work was carried out by making surface tension measurements, using a sessile mercury drop, in solutions of a fraction of polyacrylic acid (mol. wt. 7.02×10⁴) in potassium chloride at 0.01, 0.1, 0.2, and 0.5 m at 25°C.The data have been used to evaluate the surface excesses of the polymer and of the inorganic ions. The distribution of K⁺ and Cl^– in the electrical double layer and the contact adsorption of Cl^– on the mercury were very little affected by the presence of the polymer. The surface excess of polymer was always found to be greatest at low concentrations, to decrease steeply at first as the concentration was increased and then to decrease more slowly at higher concentrations.Possible explanations of this behaviour are discussed and it is concluded that the rapid decrease is a consequence of molecular weight dispersion and the stronger adsorption of high molecular weight polymer. The slow decrease in surface excess at higher concentrations may be a result of configurational changes of the polymer molecules.Surface pressure data show that, despite this decrease in the surface excess, the surface coverage reaches a high level at very low polymer concentrations and then continues to increase slowly as the concentration of polymer is increased. This apparent contradiction is due to changes in configuration of the adsorbed polymer molecules. At higher bulk concentrations the chain configurations are more compact and each adsorbed molecule makes more contacts with and so occupies a greater area of the mercury surface than at low concentrations.The conclusion is reached that the surface excess of polymer is mostly contained in a layer probably more than 1000 Å thick. It consists of a concentrated and entangled mass of polymer chains. Relatively few of these chains are in contact with the mercury at any istant. The concentration in this surface layer decreases steadily with increasing distance from the mercury surface and it merges without discontinuity into the bulk solution.With 10 figures in 22 details     

Die F?llung von Vanadium mit Phenarsazins?ure

Zusammenfassung Es wird über die Möglichkeit einer Bestimmung des Vanadat-Ions mit Phenarsazinsäure berichtet. Vanadat fällt mit dem Reagens in saurem Medium bei p_H 2 als hellbrauner flockiger Niederschlag quantitativ aus, wenn ein mehr als dreifacher molarer Überschuß an Phenarsazinsäure angewendet wird. Die Bestimmung des Vanadiums im gebildeten Niederschlag erfolgt maßanalytisch. Über einige Trennungsmöglichkeiten wird berichtet.