  We investigate the evolution of the momentum distribution of a Bose-Einstein
condensate subjected to an external small oscillatory perturbation as a
function of the in-trap evolution of the condensate after the external
perturbation is switched-off. Besides changing its momentum distribution, we
observe that the cloud distributes the input energy among its normal collective
modes, displaying center-of-mass dipolar mode and quadrupolar mode. While the
dipolar mode can be easily disregarded, we show that the momentum distribution
is closely tied to the quadrupolar oscillation mode. This convolution hinders
the actual momentum distribution.
