Physics and chemistry with diatomic molecules near absolute zero

Simple molecules can be manipulated near absolute zero with quantum optical techniques that were originally developed for atomic gases. Molecules, however, present us with profoundly distinctive properties that arise from their internal complexity and a higher density of states. They can be sensitive to different aspects of fundamental physical laws than atoms are. Here we show how a combination of molecular spectroscopy in the style of optical atomic clocks and modern quantum chemistry explain some bizarre properties of loosely bound molecules, shed light on the quantum aspects of the most basic chemical reactions, and promise to advance table-top fundamental physics in new directions.​​