Sisyphus Laser Cooling of a Polyatomic Molecule
Physicists considering a foray into the study of molecules are often warned that “a diatomic molecule is one atom too many!”. Now John Doyle and colleagues at Harvard University have thrown this caution to the wind and tackled laser cooling of a triatomic molecule with success, opening the door to the study of ultracold polyatomic molecules.
The technique of laser cooling, which uses the scattering of laser photons and the concomitant momentum transfer to bring atoms to a near halt, has revolutionized atomic, molecular, and optical (AMO) physics. Laser cooling and an important variant known as Sisyphus cooling underpin three Nobel prizes in physics - for magneto-optical trapping (1997), Bose-Einstein condensation (2001), and the manipulation of individual quantum systems (2012) - and are crucial to a host of quantum-assisted technologies and fundamental physics measurements.
Since photons carry very little momentum and therefore reduce an atom’s velocity by just a small amount, a prerequisite for effective laser cooling is the ability to scatter thousands of photons. Thus laser cooling has predominantly been used only to cool simple atoms, whose electronic structure dictates that after a photon is absorbed, spontaneous emission places the atomic electron back into its original state, allowing the process to repeat nearly ad infinitum...
Continue reading "A Diatomic Molecule Is One Atom Too Few" by Paul Hamilton and Eric R. Hudson, Physics 10 (2017). https://physics.aps.org/articles/v10/43.
Also read the original article: I. Kozyryev, L. Baum, K. Matsuda, B. L. Augenbraun, L. Anderegg, A. P. Sedlack, and J. M. Doyle, "Sisyphus Laser Cooling of a Polyatomic Molecule," Physical Review Letters 118, 173201 (2017). DOI: 10.1103/PhysRevLett.118.173201.