physique atomique L3 physique des matériaux par Pr MERAD

Atomic physics is the branch of physics that studies:

1. The atom as an isolated system, in particular:

   • Its internal structure (nucleus, electrons, electron cloud).

   • Its energy levels (quantum states of electrons).

   • Its interactions with individual particles (photons, electrons, other light atoms) and external fields.

2. Atomic processes:

   • Emission and absorption of light (spectroscopy).

   • Ionization and recombination.

   • Atomic collisions.

   • Effects of electric and magnetic fields on the atom (Stark and Zeeman effects).

Important Distinction:

• Atomic physics focuses on the atom as a whole (especially the electron cloud). Its typical scale is the angstrom (10⁻¹⁰ m).

• Nuclear physics specifically studies the atomic nucleus (protons, neutrons).

• Molecular physics studies systems formed by several bonded atoms (molecules).

Origin and Importance:
Born from the Bohr model (1913) and the development of quantum mechanics, it is fundamental for understanding:

• The nature of matter.

• Optical phenomena and lasers.

• Spectroscopy (chemical analysis, astrophysics).

• Modern technology (atomic clocks, quantum sensors, quantum computers).

In summary, atomic physics explores the behavior and properties of atoms, forming the bridge between the physics of the subatomic world (nuclear and particle physics) and that of the macroscopic world (condensed matter, chemistry).

Atomic physics is a field that deals with phenomena related to the atom and its properties, on the atomic scale. This discipline is at the origin of all quantum physics, and it played an absolutely decisive role in physics throughout the 20th century. Nowadays, this field covers a very broad area, and its developments are ultimately dispersed across many specialties. For example: magnetism, the optical properties of solids, chemical analysis, magnetic resonance imaging, lasers...