Emission peak position on the apparent energy scale is a function of the number of photons created in the radioactive decay process. The sample, which is the detector in liquid scintillation (LS) spectroscopy, may contain quenching substances. These inhibit creation of photons and, consequently, radionuclide emission peak shifts towards lower channels. Identification of the radionuclide by its peak position is therefore not straightforward under variable quench in LS spectroscopy. The end point of the Compton spectrum (or external standard quench parameter SQP(E)) gives a direct measure of the sample quench. It is normally used in LS spectroscopy for the measurement of counting efficiency. Because SQP(E) does not depend on the sample emission energy, it can be used in verification of the peak energy together with the peak position. Two known energy calibration lines are required as a function of quench to verify the peak energy.
Authors:R. S. Addleman, M. J. O’Hara, J. W. Grate, and O. B. Egorov
Direct alpha-energy spectroscopy in liquids is possible by placing a chemically selective polymer thin film upon the surface of passivated silicon diodes. By utilizing polymer thin films with high affinity for actinides, we have been able to selectively concentrate actinides of interest upon the diode surface, resulting in a substantial increase in sensitivity relative to a direct measurement. With this film coated diodes, we were able to obtain in-situ alpha spectra with energy resolution comparable to that of conventional alpha-spectroscopy. The response of the thin film coated diode was found to be linear over 104. The sensitivity and reversibility is a function of the membrane complexation chemistry.
Based on a functional description of the standard Ge(Li) spectrometer some of its shortcomings at high counting rates are
discussed and, as a possible solution to the problem, an outline is given of an experimental high rate gamma spectroscopy
with real time compensation of counting losses.
Using UV absorbance spectroscopy in determining sublimation rates has the advantage of eliminating the surface area from the rate of mass loss equation. In addition, most importantly, the relatively small scanned area ensures extremely accurate
Fe/OOCH/2.2HCOOH obtained by solvolytic reaction of FeCl2.4H2O in formic acid was studied by Mössbauer spectroscopy. It displays two quadrupole doublets. Upon air contact it easily transforms to a high-spin octahedral iron/III/ complex, whereas Fe/OOCH/2.2H2O undergoes a very slow oxidation. The formate complex coordinated with pyridine could not be prepared, instead we obtained the anhydrous phase Fe/OOCH/2.
The review discusses various analytical chemical applications of the Mössbauer effect. The labelled atoms used are Mössbauer
isotopes and the measured parameters for analysis are those of the Mössbauer spectra. High efficiency of the technique is
demonstrated by examples in studies of the structure of compounds, polyfunctional with respect to the Mössbauer element, and
of the mecahnism of chemical reactions, first of all, low-temperature solid phase reactions. The application of the emission
Mössbauer spectroscopy is also discussed for analytical purposes.