Daniel Berenyi

Search for positons in the decay of 143Pm, 144Pm and 146Pm

Abstract A coincidence method was used for detecting annihilation radiation in the research for positons in the decay of 143 Pm, 144 Pm and 146 Pm nucleides. The activities of these three isotopes contained in the source were determined from an analysis of the gamma spectrum. The source was obtained by chromatography separation from Ta, Er and Gd targets irradiated by 660–680 MeV protons. The number of positons per decay was determined to be −6 for 143 Pm , −5 for 144 Pm and −4 for 146 Pm . These limits are lower by several orders of magnitude for the first two nucleides than previously published data. No data have been published for 146 Pm. From these values the upper limits for the total disintegration energies are 1122, 2635 and 1982 keV for 143 Pm, 144 Pm and 146 Pm, respectively.

X-ray photoelectron spectroscopic investigation of electrochemically oxidised and reduced platinum surfaces

Abstract The growing of oxide layer with the time of anodic oxidation in 1M, 3.5M and 8.8M perchloric acid solutions has been investigated by XPS on smooth and platinised Pt surfaces. Pure metallic Pt surfaces were prepared by acidic digestion, ignition and cathodic reduction, and their electron spectra have been compared. The presence of a single species, probably PtO, can be evaluated from the XPS measurements. Calculated values of PtO film thickness for different time intervals of electrolytic oxidation are given at various concentrations of HClO 4 .

Inner-shell ionization by electrons in the 300–600 keV region

A measuring set-up at a Cockcrof—Walton accelerator is described for the determination of electron impact inner-shell ionization cross-section detecting the X-rays by Si(Li) solid-state detector. The K-shell electron impact ionization cross-sections for Ag in the region from 300 to 600 keV were determined and compared with the earlier experimental and the calculated theoretical values.

Problems and results in theoretical and experimental investigations of the ϵ/β+ ratio

Abstract The present state of the theory and the experiment concerning the electron capture to positon emission ratio is given. The experimental methods and procedures are also reviewed. Possible application of the determination of the ratio and some open problems in connection with it are discussed especially in the case of forbidden transitions.

Experiences on the application of the sum-coincidence method

Abstract For the study of cascade γ-processes. Hoogenbooms sum-coincidence method 1 ) has proved exceedingly useful. This method has made it possible to detect transitions of very low intensity, and possesses advantages for measurements of angular correlation as well. As the authors experience shows, in the sum-coincidence spectrum, false peaks or background levels of a certain height may appear in part of the discrimination region. This is partly due to instrumental reasons, partly to the characteristics of the method itself, and it depends on the properties of the decay scheme under study.

A critical study of the internal bremsstrahlung spectrum from 32P

Abstract An experimental study of the IB spectrum from 32 P was carried out for the clarification of the contradictions among the various experimental investigations. This study was based on a critical analysis of the measuring conditions and the evaluation process. The “classical” absorption as well as the magnetic deflection method for the elimination of the distortion effect of the electrons coming from the source (i.e. the external bremsstrahlung) were used in the same experiment. Special care was taken to eliminate the sources of possible systematic errors. As a result of this study, the observed maximum deviation of the experimental distribution from the KUB-Nilsson theory was about 6 % in the energy region from 60 to 1060 keV. Other recent experiments lead to deviations from this theory amounting to 30–40 % and 80–100 %. The probable reasons of these deviations are also discussed in the present paper.

Investigations of the decay-scheme of Fe59

Abstract We have examined the gamma-ray spectrum and gamma-gamma coincidence spectrum of Fe59 by means of scintillation spectrometers. The two lines of high energy have been found to be 1.08 and 1.27 MeV respectively. Between these lines no genuine coincidence could be detected. It was the analysis of beta spectrum and beta-gamma coincidence spectra which yielded the beta groups of 275±5 and 455±5 keV end-point energies. The intensity of these was 44.6 and 55.4% respectively, and their corresponding log ft values were 5.3 and 6.1. The relative intensity of the high energy beta transition directly into the ground state was found not to attain 0.5%.

β−γ coincidence spectrometric investigation of the decay-scheme of Nd147

Beta-gamma ray coincidence investigations were made by means of a magnetic spectrometer and a NaI(Tl) scintillation gamma-ray spectrometer incorporated into the former one in order to determine the number and maximum energy of partial beta-ray spectra at the decay of Nd/sup 147/. The following beta-ray groups of end point energy were found: 815 plus or minus 1O, 529 plus or minus 25, 365 plus or minus 15, and 215 plus or minus 15 kev. (auth)

The details of the critical study of the internal bremsstrahlung spectrum from32P

On the basis of a critical analysis of the measuring conditions and the evaluation process in the measurement of the internal bremsstrahlung (IB), an experimental study of the integral IB spectrum from32P was carried out. To eliminate the sources of possible systematic errors both in the measurement and in the evaluation, special care was devoted to the following items. 1) To check the effect of external bremsstrahlung (EB), the magnetic deflection and the “classical” absorption method for the elimination of direct electrons of the source were applied in the same experiment. 2) The detector efficiency (photopeak efficiency) for the correction of the spectrum was determined experimentally using the IAEA, Vienna, standards with known activities (errors from 1 to 3%). 3) The correction for the detector resolution was carried out by the method ofOwen andPrimakoff instead of the mostly usedLidén—Starfelt procedure. 4) With the geometrical arrangement of the experiment a low Compton distribution (relative to the photopeak) in the spectra of the monoenergetic gamma rays was provided with practically no backscatter peak. 5) The theoretical spectrum was converted into pulse-height distribution. 6) The experimental and theoretical spectrum shape was compared by normalization of the distributions to avoid errors. arising from the absolute determination of beta activity of the source.As a result of the investigation, the observed maximum deviation of the experimental distribution from theNilsson-corrected KUB theory of IB was about 6% in the energy region from 60 to 1060 keV. Even if the possible maximum errors are taken into consideration, the deviation from the KUB-Nilsson theory cannot be more than 15% in the above region in contrast with e.g. recent contradictory results [21, 22] in one of which a deviation amounting to 30–40% from the KUB-Nilsson theory was observed in the region from about 100 keV to 800 keV, while an agreement was found for higher energies up to about 1200 keV, and in the other an increasing disagreement with the above mentioned theory was indicated from 500 keV towards the higher energies up to about 1300–1400 keV (the deviation is about 80% at 1000 keV). At the same time, the present measurements definitely disprove the considerable disagreements (the greatest disagreement ever observed from the theory in an IB study) which were found in the only earlier experiment of this kind [17] where the direct electrons from the source were prevented to reach the gamma-ray detector by applying a magnetic field.РезюмеПроводя критический анализ условий измерений и обработки данных внутреннего тормозного излучения описывается эксперименальное изучение интегрального спектра внутреннего тормозного излучения32P.

Internal bremsstrahlung in the superallowed decay of the positon emitter 11C

Abstract The internal bremsstrahlung in the superallowed decay of the β + -emitter 11 C has been studied in order to check the fundamental concept of the internal bremsstrahlung process.