11,364 research outputs found

    Ground Band and a Generalized GP-equation for Spinor Bose-Einstein Condensates

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    For the spinor Bose-Einstein condensates both the total spin SS and its Z-component SZS_{Z} should be conserved. However, in existing theories, only the conservation of SzS_{z} has been taken into account. To remedy, this paper is the first attempt to take the conservation of both % S and SZS_{Z} into account. For this purpose, a total spin-state with the good quantum numbers SS and SZS_{Z} is introduced in the trial wave function, thereby a generalized Gross-Pitaevskii equation has been derived. With this new equation, the ground bands of the 23^{23}Na and % ^{87}Rb condensates have been studied, where the levels distinct in SS split. It was found that the level density is extremely dense in the bottom of the ground band of 23^{23}Na, i.e., in the vicinity of the ground state. On the contrary, for 87^{87}Rb, the levels are extremely dense in the top of the ground band,Comment: 7 page, 5 figure

    Repeating head-on collisions in an optical trap and the evaluation of spin-dependent interactions among neutral particles

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    A dynamic process of repeating collisions of a pair of trapped neutral particles with weak spin-dependent interaction is designed and studied. Related theoretical derivation and numerical calculation have been performed to study the inherent coordinate-spin and momentum-spin correlation. Due to the repeating collisions the effect of the weak interaction can be accumulated and enlarged, and therefore can be eventually detected. Numerical results suggest that the Cr-Cr interaction, which has not yet been completely clear, could be thereby determined. The design can be in general used to determine various interactions among neutral atoms and molecules, in particular for the determination of very weak forces.Comment: 15 pages, 7 figure

    Two-body scattering in a trap and a special periodic phenomenon sensitive to the interaction

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    Two-body scattering of neutral particles in a trap is studied theoretically. The control of the initial state is realized by using optical traps. The collisions inside the trap occur repeatedly; thereby the effect of interaction can be accumulated. Two periodic phenomena with a shorter and a much longer period, respectively, are found. The latter is sensitive to the interaction. Instead of measuring the differential cross section as usually does, the measurement of the longer period and the details of the periodic behavior might be a valid source of information on weak interactions among neutral particles.Comment: 5 pages, 5 figure