Application of the sum peak method to study perturbed angular correlation parameters as a function of pH value and gelatin concentration in the decay of160Dy

The - sum peak method based on the phenomenon of perturbed angular correlation has been applied to see the effect of chemical environment on the directional correlation coefficients of various cascades and to check the suitability of¹⁶⁰Tb as a probe. No change in sum peak intensity ratios for different pH and gelatin concentration values have been seen.     

Determination of perturbed angular correlation parameters in some compounds of133Ba using the sum peak method

The sum peak intensity relative to its single peak was determined in various compounds of¹³³Ba by the technique of gamma-ramma-ray sum peaks observed in a single HPGe detector. The change in intensity ratio was used to determine the time integral perturbed angular correlation coefficients for BaCl₂, Ba(NO₃)₂, BaSO₄, Ba-EDTA, Ba-MES and Ba-BSA compounds.     

Determination of perturbed angular correlation parameter\overline {G_{22} } for111In in hydrochloric acid solutions by the sum peak methodfor111In in hydrochloric acid solutions by the sum peak method

Application of the sum peak method to indium solutions in hydrochloric acid has been studied. A calibration line to determine a PAC parameter \(\overline {G_{22} } \) has been adopted using two samples with known values of \(\overline {G_{22} } \) . The results show feasibility of the method because of its simplicity and of smaller amounts of radioactivity required in the measurement compared to the ordinary PAC method.     

Semi-theoretical approach to the applications of the sum peak method

Although application of the sum peak method to determine the PAC parameter was limited to point source like specimens, a theoretical consideration has been made to examine the possibility of application of the sum peak method to specimens with finite dimension in this work. It has been revealed that the sum peak method can be applied to those specimens in the same manner as to point source like ones. Furthermore, the possibility of application of the sum peak method to determinations of the time differential attenuation factor G₂₂/t/ has been discussed, and its procedure has been proposed.     

Some applications of perturbed angular correlation and positron annihilation to materials science

The perturbed angular correlation (PAC) and positron annihilation spectroscopy (PAS) that use nuclear probes to characterize the micro-structure of materials are briefly described. Three examples are given to show their partial applications. The first example is the study of radiation damage in Si irradiated by fast neutrons of 1.45·10²⁰ cm⁻² and ¹⁷⁸W heavy ions of 5·10¹¹ cm⁻², respectively. The PAC and PAS measurements all show that the monovacancy-oxygen complexes and divacancies and divacancy-oxygen complexes were produced by the irradiations, and quadrivacancies and quadrivacancy-oxygen complexes were formed during thermal annealing. The second one illustrates the investigation of high T _c superconductivity for YBaCuO. The PAS experiment found the charge transfer during the superconducting trasition. The PAC measurement suggested a transition of two-to one-dimensional Cu-O-Cu chain structure at the superconducting trasition temperature T _c , which favors the charge transfer from the CuO layer to the CuO chain in YBaCuO. The third one is for investigating the hydrogen behavior in Pd_0.75Ag_0.25-H _x as functions of temperature from 77 K to RT and hydrogen concentration (x) from 0 to 35 at.%. The PAC and PAS results exhibit that hydrogen atoms are congregated into the hydrogen bubbles and the hydrogen bubbles grow with the increasing of the hydrogen concentration in Pd_0.75Ag_0.25-H _x . These examples demonstrate that the PAC and PAS techniques are very sensitive and powerful tools in materials science, which can well investigate phenomena in materials on atomic scale.     

The time differential perturbed angular correlation study of binding of hafnium to humic acid and its model compound

Time differential perturbed angular correlation (TDPAC) spectroscopy has been used to study the binding of hafnium to mandelic acid, which is a model compound of humic acid. The Fourier transform of TDPAC spectrum of Hf–mandelate complex showed two ω values, namely, ω_Q1 = 77 (±0.4) Mrad/s and ω_Q2 = 111 (±3.1) Mrad/s. The asymmetry parameters for the two sites were found to be 0.7 and 0.3, respectively. The electric field gradient (EFG) around the metal ion was theoretically calculated using the computer code GAMESS. The calculated EFG value was found to be in reasonable agreement with that deduced from experiment. Contrary to Hf–mandelate, the TDPAC spectrum of Hf–humate system did not show characteristic features of discrete binding sites.     

Application of the sum peak method to determine electric field gradient in different environments of133Cs nucleus

The sum peak method based on the phenomenon of perturbed angular correlation has been applied to study the nuclear quadrupole interaction frequencies at¹³³Cs which is followed by electron-capture decay of¹³³Ba. These values are used to determine the z-component, which is the largest one of the electric field gradient. The electric field gradient /EFG/ is found to vary with different compounds of barium. The method is found to be useful in describing the chemical influences on the attenuation of angular correlations and hence in the study of EFG.     

Probing electronic environment in gamma irradiated sodium borosilicate glass and simulated waste glass: a perturbed angular correlation spectroscopy study

Journal of Radioanalytical and Nuclear Chemistry - Time Differential Perturbed Angular Correlation (TDPAC) has been used to investigate the local structural changes (if any) in Sodium borosilicate...     

Electric field gradients in various chemical environments of133Ba by the sum peak method

The sum peak at 437 keV (356+81 keV) has been measured in various chemical and physico-chemical environments. The fact that the intensity ratio of the sum peak to its single peak changes with the circumstances in which the radioactive source is placed is used to observe the effect of the chemical environment on directional correlation coefficients of 351–81 keV cascade in¹³³Ba−¹³³Cs decay and to detect the variations in the electric field gradient in different barium compounds. The sum peak method has been found to be useful in describing the chemical influences onG ₂₂ parameters and hence in the study of electric field gradients.     

Practical method for the definition of chromatographic peak parameters in preparative liquid chromatography

A practical method was established for the definition of chromatographic parameters in preparative liquid chromatography. The parameters contained both the peak broadening level under different amounts of sample loading and the concentration distribution of the target compound in the elution. The parameters of the peak broadening level were defined and expressed as a matrix, which consisted of sample loading, the forward broadening and the backward broadening levels. The concentration distribution of the target compound was described by the heat map of the elution profile. The most suitable stationary phase should exhibit the narrower peak broadening and it was best to broaden to both sides to compare to the peak under analytical conditions. Besides, the concentration distribution of the target compounds should be focused on the middle of the elution. The guiding principles were validated by purification of amitriptyline from the mixture of desipramine and amitriptyline. On the selected column, when the content of the impurity desipramine was lower than 0.1%, the recovery of target compound was much higher than the other columns even when the sample loading was as high as 8.03 mg/cm³. The parameters and methods could be used for the evaluation and selection of stationary phases in preparative chromatography.     

Coordination geometry of cadmium at the zinc and copper sites of superoxide dismutases: a study using perturbed angular correlation of gamma-rays from excited 111Cd.

111Cd time-differential perturbed gamma-gamma angular correlation (PAC) has been used to investigate the Zn site in yeast and bovine copper and zinc-containing superoxide dismutases by substitution of the zinc ions with excited 111Cd(2+) ions. The PAC spectra obtained from the enzymes in aqueous solution reveal a single coordination geometry of 111Cd(2+) showing that the coordination of 111Cd(2+) to the Zn site in the two subunits is identical. Furthermore, the PAC spectra of the yeast and bovine enzymes show that the Zn sites are very similar in the two enzymes. The PAC experiments show a clear difference depending on whether the copper ion is in the oxidized or the reduced state. In the latter case the results resemble those obtained for derivatives with no metal ion at the Cu site. Hence the coordination geometry of the Zn site in these two situations must be similar, and it is very unlikely that the imidazole ring of His61 bridges the two metal ions in the reduced enzyme. The PAC spectrum of 111Cd(2+) ions at the Zn site with copper(II) ions at the Cu site is in agreement with that predicted by applying the angular overlap model (AOM) to the known crystal structure of the bovine enzyme, with known nuclear quadrupole interactions for the ligands involved. Furthermore results from experiments with copper in the reduced state show that reduction of the copper ion causes a significant change at the Zn site. An explanation for this conformational change has been proposed by computer modelling. The PAC experiments also show that it is possible to incorporate cadmium ions into the Cu site in the absence of copper ions, and the result has also been interpreted in terms of the AOM.     

Fitting the boron peak and resolving interferences in the 450–490 keV region of PGAA spectra

Prompt gamma activation analysis (PGAA) is one of the most powerful analytical methods for the determination of boron because of its very large neutron capture cross section. The peak of boron in the PGAA spectra is highly broadened due to the Doppler-effect. An improved method is presented to fit the boron peak, and to resolve interference with the gamma-rays of sodium and other matrix components. The method has been checked on test samples and on geological samples as well.     

A study on the free-radical evolution and its correlation with the optical degradation of 170 keV proton-irradiated polyimide

In this paper, the damage process was investigated on the 170 keV proton-irradiated polyimide, based on the evolution of free radical and its correlation with degradation of the optical transmittance using electron paramagnetic resonance (EPR) and optical-transmittance measurements. The results indicate that the g value of irradiated free radicals keeps at a constant of 2.0025 but the spectral intensity of the free radicals increased with the increasing proton fluence. It is found that during the post-storage after irradiation, the concentration of free radical decreased in an exponential rule with the post-storage time and the free-radical stability can be defined by the corresponding time constant at around 2.3 h. It is interested that the recovery of optical-transmittance follows the same mode as that of free radicals. The mechanisms on the free-radical evolution and the correlation between free radical and optical property are discussed in the paper.     

On the use of ligand field parameters in the study of coordinated water molecules in Eu3+ complexes

A new methodology is proposed by which the number of coordinated water molecules, n, can be estimated in Eu(3+) complexes. It is based on a comparison between the theoretical and experimental Stark levels, the former being calculated by assuming that n varies from 0 to 4 and predicting the so-called ligand field parameters, . The methodology, initially developed in the study of the Eu(pya)(3).nH(2)O complex, has been applied successfully to beta-diketonate complexes of Eu(3+), for which crystallographic and luminescence data are available.     

A software package for the evaluation of peak parameters in an analytical signal based on a non-linear regression method

Computer-based data handling of analytical signals to extract commonly used analytical parameters often produces poor results if the signals are affected by noise and a drifting baseline. Only a minor part of the information present in the signal is used for correction. A computer package is presented, in which the total information of the signal is used to give accurate evaluation of analytical parameters. The program uses a non-linear regression method to deconvolute analytical signals into a number of peaks and a baseline. To describe the peak shape any mathematical model can be used. In the computer package, a Gaussian curve-related model is used, with variable asymmetry. The baseline is described with a polynomial of variable order. The method is simultaneously a filter procedure Deconvolution of poorly separated peaks is possible. The software is developed on a minicomputer; however, test results of this study indicate the feasibility of implementation on a microcomputer without extremely time-consuming runs of the program.     

Application of the generalized standard addition method to correction for the effects of peak overlap and intermetallic compound formation in potentiometric stripping analysis

Applications of the generalized standard addition method in potentiometric stripping analysis are presented. Accurate quantitative results can be obtained, even when the analytical signals are strongly affected by peak overlaps or by the formation of intermetallic compounds. The possibilities and limitations of the approach are discussed. An optimized experimental procedure for correction of the copper-zinc intermetallic interference is introduced.