Attractive Bose-Einstein condensation in a finite trap and instability of ground state energies

The energies of Bose-Einstein condensate of Rb-85 atoms confined by the 3-dimensional parabolic and quartic trap are investigated. The two-body correlations among atoms are taken into calculation in many-body approach. We increase the number of bosons within the anharmonic trap and study the behaviour of different zero-temperature energies in detail. The interatomic interaction strongly depends on the anharmonic coefficient (lambda) as the collapsing point is observed to be varying for different values of lambda. For weak values of lambda, we observe similar behaviour of energies, as studied for harmonically trapped attractive condensate. However, when the anharmonic distortion is high, dramatic behaviour of energies near the collapsing point is observed. It is shown that the anharmonic effect is very crucial to propel the condensate towards collapsing.