Characteristic frequency of the magnetic radiation of spinor condensates

The magnetic radiation of the fully-condensed states of $^{23}$Na condensates have been studied. A narrow characteristic spectral line with a wave length proportional to N^(-2/5) (N is the number of particles) and with a probability of transition proportional to N^(17/5) emitted (absorbed) by the condensate was found. It implies that short wave radiation with a huge probability of transition can be obtained if numerous atoms are trapped. A new technique developed by the authors, namely, the analytical forms of the fractional parentage coefficients, was used to calculate analytically the matrix elements between the total spin-states.Comment: 7 pages, 5 figure

Spin evolution of spin-1 Bose-Einstein condensates

An analytical formula is obtained to describe the evolution of the average populations of spin components of spin-1 atomic gases. The formula is derived from the exact time-dependent solution of the Hamiltonian $H_{S}=c mathbf{S}^{2}$ without using approximation. Therefore it goes beyond the mean field theory and provides a general, accurate, and complete description for the whole process of non-dissipative evolution starting from various initial states. The numerical results directly given by the formula coincide qualitatively well with existing experimental data, and also with other theoretical results from solving dynamic differential equations. For some special cases of initial state, instead of undergoing strong oscillation as found previously, the evolution is found to go on very steadily in a very long duration.Comment: 7 pages, 3 figures