Focusing ground-state atoms with an electrostatic field

Wolfgang Ketterle, David E. Pritchard

Juris G. Kalnins, Jason Amini, Harvey Gould

An electrostatic lens with three focusing elements in an alternating-gradient configuration is used to focus a fountain of cesium atoms in their ground (strong-field-seeking) state. The lens electrodes are shaped to produce only sextupole plus dipole equipotentials which avoids adding the unnecessary nonlinear forces present in cylindrical lenses. Defocusing between lenses is greatly reduced by having all of the main electric fields point in the same direction and be of nearly equal magnitude. The addition of the third lens gave us better control of the focusing strength in the two transverse planes and allowed focusing of the beam to half the image size in both planes. The beam envelope was calculated for lens voltages selected to produced specific focusing properties. The calculations, starting from first principles, were compared with measured beam sizes and found to be in good agreement. Application to fountain experiments, atomic clocks, and focusing polar molecules in strong-field-seeking states is discussed.

Patrick F. O’Mahony

Jun Kobayashi, Kosuke Shibata, Takatoshi Aoki +2 more

Abstract We propose a new kind of spin manipulation method using a fictitious magnetic field generated by a quasi-electrostatic field. The method can be applicable to every atom with electron spins and has distinct advantages of small photon scattering rate and local addressability. By using a CO2 laser as a quasi-electrostatic field, we have experimentally demonstrated the proposed method by observing the Rabi-oscillation of the ground state hyperfine spin F = 1 of the cold 87 Rb atoms and the Bose-Einstein condensate. PACS: 32.90.+a, 03.75.Mn, 32.10.Fn, 32.10.Dk 1

T. Takekoshi, R. J. Knize

We demonstrate a quasi-electrostatic trap for cold Cs atoms, using a focused 20-W CO(2) laser beam (lambda = 10.6 microm). Excluding background gas collisions, we measure a trap loss rate of 0.30(33) atoms/s, which is consistent with the calculated photon-limited loss rate of 3 x 10(-11) atoms/s. We measure a ground-state hyperfine population relaxation lifetime of at least 10 s.