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Nuclear Physics 1
Nuclear Deexcitations, Spontaneous Nuclear Reactions
Ibrahima Sakho
First published 2021 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
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John Wiley & Sons, Inc.
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USA
© ISTE Ltd 2021
The rights of Ibrahima Sakho to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.
Library of Congress Control Number: 2021945496
British Library Cataloguing-in-Publication Data
A CIP record for this book is available from the British Library
ISBN 978-1-78630-641-8
Preface
Nuclear physics is devoted to the study of the properties of atomic nuclei. These properties relate to the internal structure of the nucleus which facilitate the understanding of the properties of nucleons (neutrons and protons), the mechanisms of nuclear reactions (spontaneous or induced), in order to describe the different processes of elastic and inelastic nucleus-nucleus interactions, the fields of application of nuclear physics and, finally, the impact of nuclear radiation on human health and the environment.
In general, nuclear physics is the physics of low energies, ranging from 250 eV to 10 GeV [SAO 04, GER 07, LAL 11]. The range of energies above 10 GeV [SAO 04, GER 07, LAL 11] relate to the physics of high energies whose purpose is to study the constituent particles of matter and the fundamental interactions between them. In this field, experimenters use particle accelerators that operate at very high energies or deliver very large beam intensities, thus allowing access to the fundamental laws of subatomic physics at very short distances. The most spectacular achievement to date is of course the Large Hadron Collider (LHC), launched in September 2008 at CERN.
Nuclear physics is an area that has experienced considerable growth since the discovery of radioactivity in 1896 by Henri Becquerel [HAL 11], well before the discovery of the atomic nucleus in 1911 by Ernest Rutherford [RUT 11]. Research in nuclear physics covers several topics ranging from subatomic particles to stars. It thus constitutes a fundamental component of physics, allowing the exploration of the infinitely large and the infinitely small [ARN 10]. In addition, nuclear physics makes it possible to understand many astrophysical phenomena such as nucleosynthesis processes (primordial, stellar and explosive) within the framework of the Big Bang model. The study of these processes allows us to understand the origin of chemical elements and to describe the evolution of supernova and neutron stars [SUR 98].
This book is the fruit of a 25-year long teaching career. Initially this was teaching final-year high-school S1 and S2 science students at Alpha Molo Baldé High School in Kolda, from 1996 to 2002. It was then at Bambey High School from 2002 to 2008 and at Maurice Delafosse Technical High School from 2008 to 2010. This was followed by 9 years at Assane Seck University, Ziguinchor, teaching final-year Physics undergraduates and, since February 2019, teaching final-year Physics and Chemistry undergraduates at the University of Thiès.
Nuclear Physics 1 consists of four chapters, as follows.
Chapter 1 is reserved for general information regarding the atomic nucleus with a view to establishing the general properties of nuclei. It begins with a presentation of the experimental facts that led to the discovery of the electron (β− particle), the proton, the neutron and the nucleus itself. It then focuses on the study of the composition and dimensions of the nucleus. Next, the nomenclature of nuclides and the stability of nuclei are studied. The chapter culminates with a series of exercises with answers.
Chapter 2 is dedicated to the study of nuclear deexcitation processes. The nuclear shell model, which offers an understanding of the discrete structure of nuclear levels, is studied in detail. Subsequently, the study examines the properties of angular momentum and parity, the processes of gamma deexcitation and internal conversion and the phenomenon of deexcitation by nuclear emission. A detailed study of the Bethe–Weizsäcker semi-empirical mass formula via the liquid-drop model and of the mass parabola equation for odd A completes the chapter and is followed by a series of exercises complete with answers.
Chapter 3 is devoted to the study of alpha (α) radioactivity. It begins with the experimental facts that led to the discovery of radioactivity itself, the discovery of α radioactivity and β− radioactivity, the discovery of the positron (β+ particle), neutrino and experiments highlighting α, β and γ radiation. The chapter goes on to focus on the study of radioactive disintegration and the properties of α decay. A series of exercises complete with answers is at the end of the chapter.
Chapter 4 is reserved for the study of β− and β+ decay modes and for the study of radioactive family trees. At the beginning of the chapter, we present the experimental facts that led to the discovery of artificial radioactivity. We then focus the development on the study of the properties of β decay and the link between β decay and decay by electron capture. In addition, double β decay and the process of atomic deexcitation by Auger effect are studied in this chapter. The study subsequently focuses on the presentation of radioactive series, enabling the introduction of the Bateman equations. The mechanism for radionuclide production by nuclear bombardment features
