Electronic Paramagnetic Resonance (EPR) spectroscopy is used for studying paramagnetic Tc2+ and Tc6+ complexes, respectively. Results of liquid and frozen solution studies are discussed as well as those obtained from single-crystal experiments. Structure and bonding properties are derived from the spectral data.
Authors:A. Bernes, J. J. Martinez, D. Chatain, and C. Lacabanne
Relaxation phenomena in polycarbonate have been explored by Thermally Stimulated Current (TSC) spectroscopy. A comparative study of transitions by differential scanning calorimetry has also been undertaken. In the sub-Tg region, the observed relaxations have been associated with the diffusion of local defects along the chains. In the glass transition region, the annealing induces the segregation of two relaxation modes: the lower temperature component associated with the unstressed amorphous phase, the higher temperature component attributed to stressed amorphous phase responsible for the modules observed in electron microscopy and X-ray diffraction.
Gamma spectroscopy with a high resolution Ge(Li) detector is used to determine243Am by its 74.7-keV gamma transition in solutions containing much higher specific activities of other actinides and fission
products. As little as 100 ppm of243Am relative to244Cm can be determined. A relative standard deviation of 1.4% was obtained for routine samples. The method is well suited for
analytical control of curium process steps because of its simplicity, speed, and reliability.
Reviewing the current status of real-time correction of counting losses in nuclear pulse spectroscopy, the pileup problem
is identified as the last question not resolved satisfactorily up to now. Correction of pileup losses in provided, at least
in principle, by the classical pulse generator method, however, severe limitations in test frequency prohibit its application
to real-time correction of counting losses. A solution is offered by the novel principle of the virtual pulse generator which
obviates the shortcomings of the classical method simply by not introducing pulses into the spectroscopy system. Instead,
the probability for pileup-free pulse processing is determined by suitable tests of the system status at arbitrarily high
test frequencies. After a discussion of the principles of the new method and its application to a real-time correction system
experimental evidence is provided for the complete correction of counting losses of more than 98% under conditions of stationary
as well as variable counting rates up to the limit of stable operation of the underlying spectroscopy system which is 800
000 c/s for an experimental high-rate gamma spectrometer.
Authors:P. Marijanović, J. Makjanić, and V. Valković
X-ray emission spectroscopy is a rapid, simple and accurate method for multielement trace analysis of water. This is accomplished by trace elements precipitation with a nonspecific chelating agent APDC (ammonium-1-pyrollidine dithiocarbamate) and filtration through a Millipore filter. In that way the uniform targets suitable for X-ray analysis were made and elements in concentrations as low as few ppb could be determined. APDC chelation over broad pH ranges for different elements in seawater is discussed. The best pH range for simultaneous determination of these elements is found. Results of analysis of seawater samples taken near the island Krk in the Adriatic sea are presented.
Authors:M. Leităo, J. Canotilho, A. Sousa, A. Pais, A. Sousa, and J. Simőes Redinha
In this paper the structural characterization of terfenadine crystallized from ethanol-water, ethanol and methanol is performed
by infrared spectroscopy. The OH stretching vibration, composed of three markedly overlapped bands, is analyzed by peak fitting.
The assignment of the hydrogen bonds was conducted making use of band parameters, spectroscopic data for CCl4 solutions, and molecular dynamics calculations from dimeric systems. Terfenadine just precipitated from solvents is never
in the highest crystalline state. This state is reached when the samples are heated at a temperature above 100C. Some amorphous
solid is coprecipitated with the crystalline phase, particularly in methanol.
Accurate assays of radioactive materials by gamma-ray spectroscopy depend on many factors, the most obvious being accurate
gamma-ray intensities. We have used radiochemical methods to prepare pure samples of actinides. One portion of each of these
samples was used to measure disintegration rates (generally by liquid scintillation counting), and the remainder was used
to obtain count rates of specific gamma-rays in a well-characterized HPGe spectrometer. These methods are illustrated by results
from studies of neptunium isotopes 237, 238, and 239.
The American National Standard "Calibration and Use of Germanium Spectrometers for the Measurement of Gamma-Ray Emission Rates of Radionuclides" has been reissued as N42.14-1999. The performance tests in it can be used to make sure that a gamma-spectroscopy program is set up correctly. The same tests can also be used to verify the improvements made by program developers. However, sometimes the tests in this ANSI standard are not enough. To satisfy certain quality assurance requirements, it is necessary to demonstrate that the results are correct either by hand calculations or by comparing the results to known values.
The results of atomic dynamics of ultrafines clusters of iron hydroxide and
Fe2O3 with average size 1–3nm are shown. The clusters were synthesised after chemical reaction in solution in micropores of sorbents and in topochemical reactions of thermal decomposition salts. Moessbauer spectroscopy studies are applicated. The effect of Surface Active Substance(SAS) on dynamics of clusters is observed. Thermodynamics and phemonologic models of dynamic state of cluster are considered and the probability of the coexistans solid-liquid state of cluster is discussed.