Unusual 180 degrees P-O-P Bond Angles in ZrP(2)O(7)

The structure of cubic ZrP(2)O(7) at room temperature has been solved and refined using a combination of modeling and high-resolution neutron powder diffraction data. The cell edge is 24.74 ?, the space group is Pa&thremacr;, and Z is 108. For those P(2)O(7) units not on a 3-fold axis, the P-O-P angles range from 134 degrees to 162 degrees. Two crystallographically distinct P(2)O(7) groups are on three fold axes with P-O-P angles thus constrained to be 180 degrees on average. The structure of cubic ZrP(2)O(7) was also refined from data taken at 227, 290, 371, 435, and 610 degrees C. The 3 x 3 x 3 superstructure present at room temperature disappears at about 290 degrees C, and all P-O-P angles of P(2)O(7) are then constrained by symmetry to be 180 degrees on average. The exceptionally low thermal expansion shown by ZrP(2)O(7) above 290 degrees C is likely related to the unusual P-O-P angle.     

103Rh-NMR-spektroskopischer Nachweis der gemischten Nonahalogenodirhodate(III), [Rh2ClnBr9–n]3−, n = 0–9

¹⁰³Rh NMR Spectroscopic Evidence of Mixed Nonahalogenodirhodates(III), [Rh₂Cl_nBr_9–n]^3?, n = 0–9 On heating a mixture of the tetrabutylammonium salts (TBA)₃[Rh₂Cl₉] and (TBA)₃[Rh₂Br₉] at 60°C in propylenecarbonate the complete system of the mixed nonahalogenodirhodates(III) [Rh₂Cl_nBr_9–n]^3?, n = 0–9 is formed. In the ¹⁰³Rh nmr spectra 40 different species have been detected, 16 with two equivalent ¹⁰³Rh atoms each resulting in one singlet and 24 with inequivalent ¹⁰³Rh atoms each pair giving two resonances. The signals of the geometric isomeres are not resolved. All 64 expected resonances are really observed. By additional measuring of the ¹⁰³Rh nmr spectra of the fractions n = 0–4 separable by ion exchange chromatography on DEAE cellulose, and utilizing characteristic increments of chemical shifts the complete and unambiguous assignment of all signals is achieved.     

Moisture absorption and absorption kinetics in polyelectrolyte films: influence of film thickness

Specular X-ray reflectivity (XR) and quartz crystal microbalance (QCM) measurements were used to determine the absorption of water into thin poly(4-ammonium styrenesulfonic acid) films from saturated vapor at 25 degrees C. The effect of film thickness on the absorption kinetics and overall absorption was investigated in the range of thickness from (3 to 200) nm. The equilibrium swelling of all the films irrespective of film thickness was (0.57+/-0.03) volume fraction. Although the equilibrium absorption is independent ofthickness, the absorption rate substantially decreases for film thickness < 100 nm. For the thinnest film (3 nm), there is a 5 orders of magnitude decrease in the diffusion coefficient for water.     

Properties of multiplicity distributions in νA and\bar v A intersections atE_{\begin{array}{*{20}c} {( - )} \\ v \\ \end{array} }< 30GeV

We present data on the multiplicity structure of inclusive charged hadron production in charged current neutrino and antineutrino freon interactions in the energy range 3–30 GeV resulting from an experiment with the bubble chamber SKAT. Average multiplicities, dispersions and correlation coefficients are investigated. Furthermore, KNO-scaling is studied and average net charges are calculated in different kinematical regions. Our data are compared with results from \(\begin{array}{*{20}c} {( - )} \\ v \\ \end{array} \) -interactions on an isoscalar target of “free” nucleons to study the influence of nuclear effects.