Theoretical Nuclear Physics

John M. Blatt, Victor F. Weisskopf, Victor F. Weisskopf

• Publisher: Dover Publications
• Year: 2012
• eBook ISBN: 9780486139500
• Topic: Physical Sciences
• Subtopic: Physics
• Index: Physics

A classic work by two leading physicists and scientific educators endures as an uncommonly clear and cogent investigation and correlation of key aspects of theoretical nuclear physics. It is probably the most widely adopted book on the subject. The authors approach the subject as "the theoretical concepts, methods, and considerations which have been devised in order to interpret the experimental material and to advance our ability to predict and control nuclear phenomena."
The present volume does not pretend to cover all aspects of theoretical nuclear physics. Its coverage is restricted to phenomena involving energies below about 50 Mev, a region sometimes called classical nuclear physics. Topics include studies of the nucleus, nuclear forces, nuclear spectroscopy and two-, three- and four-body problems, as well as explorations of nuclear reactions, beta-decay, and nuclear shell structure. The authors have designed the book for the experimental physicist working in nuclear physics or graduate students who have had at least a one-term course in quantum mechanics and who know the essential concepts and problems of nuclear physics.

CHAPTER I

General Properties of the Nucléus

1. INTRODUCTION

In spite of the tremendous amount of information now available about atomic nuclei, nuclear physics is a very young science. The existence of a nucleus in each atom was discovered by Rutherford (11)¹ in the year 1911. Some of the fundamental properties of nuclei were found at that time:

(1) They have radii very small compared to atomic dimensions; Rutherford showed that the nucleus acts like a point charge down to distances of the order of 10⁻¹¹ cm, at least.

(2) They are charged. The charge on each nucleus turned out to be an integral multiple of the charge on the electron, i.e., nuclear charge = Ze, where Z = 1,2,3,··· is called the atomic number.

(3) Nuclei are very heavy compared to electrons. Most of the mass in an atom resides in the nucleus.

Since atoms are neutral entities, it was necessary to assume that the charge on the nucleus is exactly neutralized by the charges of the surrounding electrons. The charge Z of the nucleus then determines the number of the electrons in the atom and is the only property of the nucleus of importance for atomic physics, and consequently for most of the properties of matter as we know it.

The next important quantity of the nucleus is its mass. J. J. Thomson (13) discovered that the mass of the nucleus is not determined by its charge. Rather, there exist nuclei of the same charge Z but of different masses. Such nuclei are called isotopes. The mass of each isotope is nearly (but not precisely) equal to an integral number of proton masses.² The nearest integer is called the “mass number” and is denoted by A.

The simplest hypothesis regarding nuclear constitution would be that all nuclei are made up of protons. This is contradicted by the fact that the mass number A is at least twice the atomic number Z in practically all nuclei. Thus other particles are needed in the nucleus besides protons.

The next hypothesis, which was current until 1932, postulated that nuclei are made up of protons and electrons. The nucleus N¹⁴ (Z = 7, A = 14), for example, was thought to consist of 14 protons (to give the correct mass) and 7 electrons (to give the correct charge). Ehrenfest and Oppenheimer (31) pointed out that this hypothesis leads to a serious contradiction with known properties of N¹⁴ (see Section 8).

The experimental discovery of the neutron (Curie-Joliot 32, Chadwick 32) led Heisenberg (32) to suggest the hypothesis that nuclei are made up of neutrons and protons and to explore the consequences of this assumption. Thus nuclear physics, as we know it today, dates back no farther than 1932.³

Under the assumption (which is very well confirmed by now) that nuclei are made up of neutrons and protons, the number of neutrons, N, in the nucleus is equal to A − Z. Neutrons and protons have nearly equal masses, and both will be referred to as “nucleons.” Nuclei with equal mass number A but different atomic number Z are called isobars or isobaric nuclei. Nuclei with equal Z but different A are called isotopes or isotopic nuclei. Nuclei with equal N = A − Z but different Z are called isotones. Isotopes are chemically equal and therefore hard to separate. From the point of view of nuclear physics, however, isotopes are nuclei with a different number of constituents. Isobars are chemically different because of their different atomic number Z. They are, however, more similar than isotopes from the nuclear point of view, since they consist of the same number of nucleons, and protons and neutrons have very similar properties within the nucleus.

The forces which hold a nucleus together cannot be ordinary electrostatic forces, since the (electrically neutral) neutrons are bound in the nucleus. The “nuclear forces,” unlike the forces which hold an atom together, have no analogy in classical physics. The fundamental steps in the exploration of nuclear forces were taken by Wigner (33a, 33b), who showed that they must have a very short range of action but must be very strong (millions of times as strong as the electr...

Table of contents

• DOVER BOOKS ON PHYSICS
• Title Page
• Copyright Page
• PREFACE
• Table of Contents
• CHAPTER I - General Properties of the Nucléus
• CHAPTER II - Two-Body Problems at Low Energies
• CHAPTER III - Nuclear Forces
• CHAPTER IV - Two-Body Problems at High Energies
• CHAPTER V - Three- and Four-Body Problems
• CHAPTER VI - Nuclear Spectroscopy I. General Theory
• CHAPTER VII - Nuclear Spectroscopy II. Special Models
• CHAPTER VIII - Nuclear Reactions: General Theory
• CHAPTER IX - Nuclear Reactions; Application of the Theory to Experiments
• CHAPTER X - Formal Theory of Nuclear Reactions
• CHAPTER XI - Spontaneous Decay of Nuclei
• CHAPTER XII - Interaction of Nuclei with Electromagnetic Radiation
• CHAPTER XIII - Beta-Decay
• CHAPTER XIV - Nuclear Shell Structure
• APPENDIX A - Angular Momentum Operators and Eigenfunctions
• APPENDIX B - Multipole Radiation
• References
• INDEX
• A CATALOG OF SELECTED DOVER BOOKS IN SCIENCE AND MATHEMATICS