Selection rules and centre-of-mass motion of ultracold atoms [chapter]

S J van Enk
Optical Angular Momentum  
In recent yeam much aaention has been paid to the quantized evolution of the centreof-mass momentum and position of ultracold atoms in light fields. We consider the effects resulting from the quantization of the extemal angular momentum variables. We investigate how spin and orbital angular momentum of light are transferred to internal and extemal angular momenhlm of an atom in dipole and quadrupole h'ansitions. dimensions [3] and to different atomic transitions [4]. Another example is the
more » ... example is the quantized motion of cold atoms in optical potential wells with the size of a wavelength, produced by two counterpropagating laser beams [SI. Here atoms can be trapped in a single well and can occupy a single quantized energy level therein. Also the occurrence of tunnelling from one well to an adjacent one has been predicted [6]. The presence of the discrete energy levels and the localization of an atom in one well have heen observed experimentally [7, 81. Recently cooling of atoms and their quantized motion in optical wells has also been observed in twoand three-dimensional laser beam configurations [9-111. Now photons also carry angular momentum [12]. Therefore, photons can exert, in addition to a force, also a torque on an atom. There is one important difference, however:
doi:10.1887/0750309016/b1142c36 fatcat:t3zs647r3bcodixvzlwqts24oy