Lecture
This lecture discusses the principles of optical absorption in gases, explaining how excited atoms emit light and how cold gases absorb light. The instructor illustrates the concept using energy diagrams and absorption lines, emphasizing the differences between emission and absorption phenomena. The lecture also covers the evolution of particles in a rectangular potential, exploring the behavior of electrons in various energy states. The instructor introduces the formation of molecules, particularly focusing on lithium, and explains how two atoms interact when brought close together. The discussion includes the concepts of symmetric and antisymmetric states, energy levels, and the significance of overlap in atomic orbitals. The lecture concludes with an overview of how multiple potential wells can lead to the formation of energy bands, transitioning from atomic to metallic states, and the implications for understanding quantum systems.