Molecular beams are cool because they create a one dimensional flow of molecules, which makes it easier to observe certain single-molecule effects, as it removes the multi-particle issues from experiments.
Key molecular beam experiments include:
- Stern-Gerlach experiment, which confirmed the existence of spin
- Rabi's NMR experiment, which confirmed the existence of nuclear spin
The center piece of the control system of atomic clocks is a molecular beam.
