  Controlling the interactions between atoms with external fields opened up new
branches in physics ranging from strongly correlated atomic systems to ideal
Bose and Fermi gases and Efimov physics. Such control usually prepares samples
that are stationary or evolve adiabatically in time. On the other hand, in
molecular physics external ultrashort laser fields are employed to create
anisotropic potentials that launch ultrafast rotational wave packets and align
molecules in free space. Here we combine these two regimes of ultrafast times
and low energies. We apply a short laser pulse to the helium dimer, a weakly
bound and highly delocalized single bound state quantum system. The laser field
locally tunes the interaction between two helium atoms, imparting an angular
momentum of $2\hbar$ and evoking an initially confined dissociative wave
packet. We record a movie of the density and phase of this wave packet as it
evolves from the inside out. At large internuclear distances, where the
interaction between the two helium atoms is negligible, the wave packet is
essentially free. This work paves the way for future tomography of wave packet
dynamics and provides the technique for studying exotic and otherwise hardly
accessible quantum systems such as halo and Efimov states.
