Quantum mechanics was discovered and built in great part by observing how light interacts with matter, in particular with atoms. This has led to the understanding of the structure of the atom. Today, this knowledge is used to manipulate atoms with laser light, leading to the new field of ultracold atom physics and its applications. The course will use multiple approaches – classical mechanics, thermodynamics, quantum physics – to build the concepts essential to the understanding of modern experiments in atomic physics. It will apply many of the concepts and techniques developed in
Quantum Mechanics 3. In particular, it will focus on the following aspects:

1. Spectral decomposition of radiation, finite linewidth mechanisms, mechanical action of light;
2. Electronic structure of atom, many electron effects, relativistic effects;
3. Quantum theory of light-atom interaction, forbidden transitions, atoms in magnetic fields.

Using all these tools and concepts, we will see how one can use lasers to cool a gas of atoms down to 100 microkelvins, and how one can trap these atoms in a magnetic bottle and further cool them down by “evaporating” them. We will also see how these ultracold atoms can make a clock which won't lose a second in 100 million years!

By the end of the module students should be able to:

• calculate and interpret light spectra,
• apply the detailed balance principle,
• describe and calculate the mechanical effects of light on atoms,
• describe or infer the atomic structure and relate it to the hierarchy of interactions,
• apply perturbation theory to atoms in external fields, infer selection rules for the coupling of light with atoms,
• describe and analyse modern atomic physics experiments