Precision measurement of spin-dependent interaction strengths for spin-1 and spin-2⁸⁷Rb atoms

Abstract

We report on precision measurements of spin-dependent interaction-strengths\nin the 87Rb spin-1 and spin-2 hyperfine ground states. Our method is based on\nthe recent observation of coherence in the collisionally driven spin-dynamics\nof ultracold atom pairs trapped in optical lattices. Analysis of the Rabi-type\noscillations between two spin states of an atom pair allows a direct\ndetermination of the coupling parameters in the interaction hamiltonian. We\ndeduce differences in scattering lengths from our data that can directly be\ncompared to theoretical predictions in order to test interatomic potentials.\nOur measurements agree with the predictions within 20%. The knowledge of these\ncoupling parameters allows one to determine the nature of the magnetic ground\nstate. Our data imply a ferromagnetic ground state for 87Rb in the f=1\nmanifold, in agreement with earlier experiments performed without the optical\nlattice. For 87Rb in the f=2 manifold the data points towards an\nantiferromagnetic ground state, however our error bars do not exclude a\npossible cyclic phase.\n