Single-atom photon recoil momentum Available to Purchase

Single-atom photon recoil momentum in a dispersive medium has been measured. Photons have no mass, but they do carry momentum, h/λ, where h is Planck’s constant and λ is the wavelength of the light in vacuum. In a dispersive medium, light’s momentum separates into electromagnetic momentum and mechanical momentum of the medium. Therefore, there has been some confusion concerning the medium’s recoil when a photon is absorbed. A group at MIT has now verified that the momentum transferred to the absorbing atom is nh/λ, with n the index of refraction. The physicists used two identical laser beams sent into a dilute Bose–Einstein condensate of rubidium atoms. The first beam placed a small fraction of the atoms into a particular momentum state within the BEC. After a delay, the second beam created more identically moving atoms that interfered with the initial batch. The resulting beat note provided the momentum...