Estudio espectroscópico de las cadenas radiactivas : Gd149 -C.E (flecha) Eu149 -C.E (flecha) Sm149 y Tb153 -C.E (flecha) Gd153 -C.E (flecha) Eu153 : cálculo de los coeficientes de conversión interna

Se realiza un estudio espectroscópico en la cadena de desintegración radiactiva gd149 eu149 sm149, usando las intensidades gamma y de electrones de conversión interna, medidas con un espectrómetro magnético de doble enfoque, se deducen los coeficientes de conversión interna, multipolaridades y sus razones de mezcla para varias transiciones de eu149 y sm149. Estos valores se comparan con datos previos de la bibliografía reciente. También se calculan valores de intensidades relativas para transiciones de sm145, pm145 y nd145 resultantes en una cadena radiactiva originada por la desintegración alfa del tb149. Se realiza un estudio similar al anterior para la cadena radiactiva tb153 gd153 eu153. En donde se obtienen los coeficientes de conversión interna para transiciones del gd153, además se obtienen intensidades gamma y de rayos x para el eu153 junto con las relaciones de intensidades de rayos x que se comparan con los resultados teóricos. Para estos trabajos ha sido necesaria la utilización de una serie de detectores (ge, si(li), espectrómetro de doble enfoque) y metodos informatizados, por lo que también se ha desarrollado un programa de análisis de espectros nucleares con el que se calculan las intensidades de las líneas gamma y se pueden separar dobletes. Se ha instalado y puesto a punto un detector de electrones sensible a posición, midiendo sus principales caracteristicas. Para la posterior reconversión del espectrómetro magnético de doble enfoque para detección multicanal con la colocación de dicho detector sensible a posición en el plano focal del espectrógrafo, este ultimo proceso haría al sistema completamente competitivo al aumentar su sensibilidad y resolucion

New process to describe radiation damage at the molecular level. Application to I-125 seeds in water

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/We present the first step of a general study on induced damage by 125I in water at the molecular level. Requirements for such a study are introduced and preliminary results on the emission spectra of 125I seeds are presented.This work was supported by MINECO (FIS2012-31230) and FCT/MEC, RaBBiT, PD-F,PD/00193/2012); UID/Multi/04378/2013 (UCIBIO); UID/FIS/00068/2013 (CEFITEC); and grant number SFRH/BD/52536/2014.Peer Reviewe

The yield of air fluorescence induced by electrons

The fluorescence yield for dry air and pure nitrogen excited by electrons is calculated using a combination of well-established molecular properties and experimental data of the involved cross sections. Particular attention has been paid to the role of secondary electrons from ionization processes. At high pressure and high energy, observed fluorescence turns out to be proportional to the ionization cross section which follows the Born-Bethe law. Predictions on fluorescence yields in a very wide interval of electron energies (eV - GeV) and pressures (1 and 1013 hPa) as expected from laboratory measurements are presented. Experimental results at energies over 1 MeV are in very good agreement with our calculations for pure nitrogen while discrepancies of about 20% are found for dry air, very likely associated to uncertainties in the available data on quenching cross sections. The relationship between fluorescence emission, stopping power and deposited energy is discussed.Comment: 27 pages, 12 figures, 64 references. Accepted in Astroparticle Physic

Energy deposition model for low-energy electrons (10–10 000 eV) in air

6 pages, 7 figures.-- PACS: 87.66.-aAn energy deposition model for electrons in air that can be useful in microdosimetric applications is presented in this study. The model is based on a Monte Carlo simulation of the single electron scattering processes that can take place with the molecular constituents of the air in the energy range 10–10 000 eV. The input parameters for this procedure have been the electron scattering cross sections, both differential and integral. These parameters were calculated using a model potential method which describes the electron scattering with the molecular constituent of air. The reliability of the calculated integral cross section values has been evaluated by comparison with direct total electron scattering cross-section measurements performed by us in a transmission beam experiment. Experimental energy loss spectra for electrons in air have been used as probability distribution functions to define the electron energy loss in single collision events. The resulting model has been applied to simulate the electron transport through a gas cell containing air at different pressures and the results have been compared with those observed in the experiments. Finally, as an example of its applicability to dosimetric issues, the energy deposition of 10 000 eV by means of successive collisions in a free air chamber has been simulated.This work has been partially supported by the Spanish Programa Nacional de Promoción General del Conocimiento (Project No. BMF 2000-0012) and by the research program of the Universidad Nacional de Educación a Distancia (Projects Nos. 2001v/proyt/04 and 20011/ininvt/37).Peer reviewe

Inelastic scattering and stopping power for electrons in O2 and O3 at intermediate and high energies, 0.3–5 keV

In this study, the stopping power for electrons in O2 and O3 molecules is reported for incident energies ranging from 300 to 5000 eV. The present results have been obtained by combining the calculated inelastic electron scattering cross-sections with an experimental energy loss procedure. Calculations have been carried out by means of a quasifree absorption model whose reliability has been checked by comparison with the electron scattering total cross section measured in a transmission beam experiment. Results for O2 are compared with high energy stopping power data available in the literature. For O3, these are the first results of the stopping power for electrons

Total and elastic electron scattering cross sections from ozone at intermediate and high energies

Total cross sections for electron scattering from O3molecules in the energy range 350-5000 eV have been measured for the first time. The experimental method used was based on the measurement of the attenuation of a collimated electron beam through an O3-O2 mixture in combination with use of an electron energy loss technique to determine the purity of the ozone sample. Differential and integral elastic cross sections have also been calculated using a scattering potential in the framework of the independent-atom model. The present theoretical and experimental results are compared with earlier calculations available in the literature

Study on Tl-204 simultaneous electron and photon emission spectra and their interaction with gold absorbers. Experimental results and Monte Carlo simulations

This work presents the experimental spectra obtained with different gold absorbers for incident electron and photon radiation induced by Tl-204. The energy spectra of beta and X-rays after penetrating gold of various thicknesses were obtained simultaneously by using a beta-X Si(Li) spectrometer without a beryllium window. Gold was chosen as the absorbent material since in recent studies an enhancement of radiation effects on biological systems has been demonstrated in the presence of gold nanoparticles, and thus the detailed microscopic description and understanding of radiation transport in this medium is becoming of high importance. This study also applied Monte Carlo codes GEANT4 and TRAX to simulate primary and secondary particle interactions in gold. Comparisons between the simulations and our corresponding experimental studies are then presented and discussed

Secondary electron interactions in materials with environmental and radiological interest

5 pags., 6 figs. -- 2. International Symposium on Low Energy Electron - Molecule Interactions; Chlewiska near Siedlce (Poland); 29 Aug - 2 Sep 2002Important environmental and radiological applications require energy deposition models including the interactions between secondary electrons and the atoms or molecules of the medium. In this work we propose a method to obtain reliable cross-section data to be used in these models by combining total and ionization cross-section measurements with simple calculations of the differential and integral elastic cross-sections. The energy loss spectra obtained in this experiment have been also used to drive stopping power of the considered materials for electrons. Some examples of results for atomic (Xe) and molecular (CF4) targets are presented and discussed in this paper.This work has been partially supported by the Spanish Programa Nacional de Promocion General del Conocimiento (Project BFM2000-0012).Peer reviewe

A process to describe radiation damage at the molecular level. Application to the 125I seeds in water

8 pags., 6 figs., 5 tabs.The correlation between the absorbed energy and the induced biological damage still has unclear aspects, especially in the low energy and low dose rate irradiation regimes. From the knowledge of the molecular-induced effects (dissociations), it would be possible to better understand the side effects of radiation, such as induced cancers or damage to healthy tissue. With this in view, this paper presents results of a simulation of a I-seed treatment with an event-by-event MC code (LEPTS) specifically designed to account for the low energy secondary particle interactions, such as electron attachment, vibro-rotational and neutral dissociation interactions. This calculation allowed us to analyze the potential radiation damage not only in connection with the energy deposition, but also in terms of induced molecular dissociations by taking into account ionizing and non-ionizing dissociative processes. We propose that this description of the molecular level damage be the basis for nanodosimetric evaluations.This work was supported by MINECO (FIS2012-31230) and FCT/MEC, RaBBiT, PD-F, PD/00193/2012; UID/Multi/04378/2013(UCIBIO); UID/FIS/00068/2013 (CEFITEC); and FCTMCTES Grant no.SFRH/BD/52536/201