PRECISION-MEASUREMENT OF H M(CS) BASED ON PHOTON RECOIL USING LASER-COOLED ATOMS AND ATOMIC INTERFEROMETRY/

The recoil of an atom due to the absorption of up to 64 photons is mea sured, using laser-cooled cesium atoms which are made to interfere in an atomic fountain. Measurement of the photon recoil allows a determin ation of HBAR/m(Cs), and hence the fine-structure constant. The measur ement is described and a detailed theoretical and experimental study o f potential systematic errors is presented. A relative precision in th e photon recoil measurement of 0.1 ppm is obtained in two hours of dat a collection. The measurement is currently 0.85 ppm below the accepted value of HBAR/m(Cs). We cannot now formally ascribe a systematic erro r, but suspect that the bulk of the discrepancy is due to imperfection s of the interferometer beams used to induce the Raman transitions.