  The dynamical behavior of Bose-Einstein condensation (BEC) in a gas with
attractive interactions is striking. Quantum theory predicts that BEC of a
spatially homogeneous gas with attractive interactions is precluded by a
conventional phase transition into either a liquid or solid. When confined to a
trap, however, such a condensate can form provided that its occupation number
does not exceed a limiting value. The stability limit is determined by a
balance between self-attraction and a repulsion arising from position-momentum
uncertainty under conditions of spatial confinement. Near the stability limit,
self-attraction can overwhelm the repulsion, causing the condensate to
collapse. Growth of the condensate, therefore, is punctuated by intermittent
collapses, which are triggered either by macroscopic quantum tunneling or
thermal fluctuation. Previous observation of growth and collapse has been
hampered by the stochastic nature of these mechanisms. Here we reduce the
stochasticity by controlling the initial number of condensate atoms using a
two-photon transition to a diatomic molecular state. This enables us to obtain
the first direct observation of the growth of a condensate with attractive
interactions and its subsequent collapse.
