Atomic physics is the subfield of physics that studies atoms as an isolated system. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change. Atomic physics can be divided into two main branches: atomic structure and atomic interactions.
The study of atomic structure is concerned with understanding the electronic configurations of atoms and how these configurations change under various external conditions. The most important tool for studying atomic structure is spectroscopy, which probes the atom’s electron energy levels and transitions between them. Other tools include lasers, electric and magnetic fields, and particle accelerators.
The study of atomic interactions focuses on how atoms interact with each other and with their environment. This includes understanding phenomena such as ionization (the process by which an atom loses or gains electrons), collisional excitation (the transfer of energy between colliding particles), and radiation emission (the release of photons from an atom). Atomic interactions are also important for applications such as semiconductor fabrication, medical diagnosis, and security scanning.