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[en] It is shown that the interface in a two-component Bose-Einstein condensate (BEC) with a dipole-dipole interaction spontaneously develops patterns similar to those formed in a ferrofluid. Hexagonal, labyrinthine, solitonlike structures, and hysteretic behavior are numerically demonstrated. Superflow is found to circulate around the hexagonal pattern at rest, offering evidence of supersolidity. The system sustains persistent current with a vortex line pinned by the hexagonal pattern. These phenomena may be realized using a 52Cr BEC.
[en] We show that in contrast with contact interacting gases, an optical lattice changes drastically the stability properties of a dipolar condensate, inducing a crossover from dipolar destabilization to dipolar stabilization for increasing lattice depths. Performing stability measurements on a 52Cr Bose-Einstein condensate in an interaction-dominated regime, repulsive dipolar interaction balances negative scattering lengths down to -17 Bohr radii. Our findings are in excellent agreement with mean-field calculations, revealing the important destabilizing role played by intersite dipolar interactions in deep lattices.
[en] Its large magnetic moment in the ground state makes chromium a good candidate for the study of dipolar interactions in a degenerate gas. We have built an experimental setup for trapping and cooling atoms of "5"2Cr down to Bose-Einstein condensation (BEC). Evaporative cooling takes place in a purely optical trap, which is loaded from the magneto-optical trap using a novel process of continuous accumulation of metastable states. We produce a condensate of typically 15000 atoms in a time of 15 s. We have studied the possibility to bring all the Zeeman substates of a chromium BEC to degeneracy in a non-zero static magnetic field, using a radiofrequency (rf) magnetic field, and demonstrated a new process of rf-assisted dipolar relaxation. We have also studied a narrow Feshbach resonance induced by dipolar interaction, which implies a d-wave collisional channel. We analyzed this resonance in the presence of a rf magnetic field and we reinterpreted rf association of molecules as a mere Feshbach resonance between rf dressed states. Finally, we have set up an optical lattice in the perspective of studying the effects of dipole-dipole interactions in reduced dimension. (author)
[en] The decay of (J/sup π/in parentheses) 52V(3+), 52Mn/sup m/(2+), and 52Mn/sup g/(6+) has been studied in order to clarify the number and nature of levels in 52Cr below 5 MeV. The levels of 52Cr that are populated in these β decays are (J/sup π/in parentheses) ground state (0+), 1434.08 (2+), 2369.60 (4+), 2767.68 (4+), 2964.77 (2+), 3113,82 (6+), 3161.63 (2+), 3415.27 (4+), 3472.2 (3+), 3615.84 (5+), 3771.8 (2+), 3951 ((1+)), 4015.42 (5+), (4208 (-)), 4563 (3-), 4627.1 (5+), and 4815.7 keV (1+,2+). A single level at 3472.2 keV (3+) replaces the previously proposed doublet at 3469 and 3473 keV
[en] Using the method to match data on stripping and pickup reactions on one and the same nucleus one obtained data on characteristics of proton single-particle states in 50,52Cr nuclei. It is shown that in terms of a spherical dispersive optical model one manages to find the systems of effective parameters of a dispersive optical potential the use of which ensures agreement of the energy calculated values with the experimental ones within the limits of the experimental errors of the experimental energy values
[ru]С использованием метода согласования данных из реакций срыва и подхвата на одном и том же ядре получены данные о характеристиках протонных одночастичных состояний в ядрах 50,52Сг. Показано, что в рамках сферической дисперсионной оптической модели удается найти системы эффективных параметров дисперсионного оптического потенциала, с использованием которых расчетные энергии согласуются с экспериментальными в пределах экспериментальных погрешностей последних