F. Biraben

Proposal for new experimental schemes to determine the Avogadro constant

We propose two experimental schemes for the determination of the Avogadro constant NA with a relative uncertainty of 10 −7 or better combining a watt balance experiment and a cold atom experiment measuring h/m(X) (where h is the Planck constant and m(X) the mass of the atom X). We give some prospects about possible uncertainties, and we discuss the opportunity to test the existence of possible unknown correction factors for the Josephson effect and the quantum Hall effect.

Determination of the fine structure constant with atom interferometry and Bloch oscillations

We report a new measurement of the atomic recoil using atom interferometry and Bloch oscillations in a vertical accelerated optical lattice. For the first time, we combine the high efficiency of Bloch oscillations with the sensitivity of Ramsey-Borde interferometer. The new determination of the fine structure constant alpha is in very good agreement with our previous non interferometric one. The uncertainties of our values of alpha are smaller than the uncertainty of any other value except those deduced from the measurements of the electron magnetic moment anomaly ae.