Atomic and molecular physics: a primer

Atoms are the basic building blocks of any material system: their physics rules over the behaviour of basically everything. Therefore, even if we limit ourselves to just consider what is found on our planet, the atomistic picture is really needed to understand at the most fundamental level the physical behaviour of organic and inorganic matter, biological molecules and systems, as well as geological materials. Accordingly, some substantial basic notion on atomic physics must be recognised as inalienable from a modern undergraduate course in physics, as well as in materials science, chemistry, and, likely, engineering too. Since the first step in atomic aggregation consists in the formation of molecules, any tutorial introduction to the topic must also necessarily contain an introduction to molecular physics. This state of affairs defines the main goal of this volume, namely: to present a modern and unified tutorial account of the fundamental physics of atoms and molecules. A modern approach does require the use of quantum mechanics, while a unified perspective dictates looking at a molecule as a bound system of atoms, still retaining some of their properties. Both features are fully exploited in this volume. This Primer is divided into three parts: the first one provides a brief historical introduction on early atomic physics and outlines the kernel of non-relativistic quantum mechanics, the second one is addressed to atomic physics, and the third one deals with molecules. Eight appendices are added to the text, each focussed on some technical development which, at first reading, can be skipped without compromising the general understanding of the arguments developed in the main text. A bibliography is added to each chapter as a guideline for further reading. The volume contains many figures, most of which are ‘conceptual’, i.e. they are basically intended to provide a graphical representation of the main ideas and concepts developed in the written part. Tables with numerical values of important physical properties are included as well, in the attempt to provide the reader with information useful to ‘quantify’ the physical results presented. Finally, a list of all the mathematical symbols used in the volume is given at the beginning as an orientation guide while reading.