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[en] We have used inelastic light scattering to study correlated phases of an array of one-dimensional interacting Bose gases. In the linear response regime, the observed spectra are proportional to the dynamic structure factor. In particular we have investigated the superfluid to Mott insulator crossover loading the one-dimensional gases in an optical lattice and monitoring the appearance of an energy gap due to finite particle-hole excitation energy. We attribute the low frequency side of the spectra to the presence of some superfluid and normal phase fraction between the Mott insulator regions with different fillings produced in the inhomogeneous systems. In the Mott phase we also investigated excitations to higher excited bands of the optical lattice, the spectra obtained in this case being connected to the single particle spectral function. In one-dimensional systems the effect of thermal fluctuations and interactions is enhanced by the reduced dimensionality showing up in the dynamic structure factor. We measured the dynamic structure factor of an array of one-dimensional bosonic gases pointing out the effect of temperature-induced phase fluctuations in reducing the coherence length of the system.

[en] We perform extensive magnetic Feshbach spectroscopy of an ultracold mixture of fermionic ⁴⁰K and bosonic ⁸⁷Rb atoms. The magnetic-field locations of 13 interspecies resonances are used to construct a quantum collision model able to predict accurate collisional parameters for all K-Rb isotopic pairs. In particular, we determine the interspecies s-wave singlet and triplet scattering lengths for the ⁴⁰K-⁸⁷Rb mixture as (-108±3)a₀ and (-205±5)a₀, respectively. We also predict accurate scattering lengths and the position of Feshbach resonances for the other K-Rb isotopic pairs. We discuss the consequences of our results for current and future experiments with ultracold K-Rb mixtures

[en] We discover several magnetic Feshbach resonances in collisions of ultracold ³⁹K atoms, by studying atom losses and molecule formation. Accurate determination of the magnetic-field resonance locations allows us to optimize a quantum collision model for potassium isotopes. We employ the model to predict the magnetic-field dependence of scattering lengths and of near-threshold molecular levels. Our findings will be useful to plan future experiments on ultracold ³⁹K atoms and molecules