  Vibrational dynamics in conventional molecules usually takes place on a
timescale of picoseconds or shorter. A striking exception are ultralong-range
Rydberg molecules, for which dynamics is dramatically slowed down as a
consequence of the huge bond length of up to several micrometers. Here, we
report on the direct observation of vibrational dynamics of a recently observed
Rydberg-atom-ion molecule. By applying a weak external electric field of a few
mV/cm, we are able to control the orientation of the photoassociated
ultralong-range Rydberg molecules and induce vibrational dynamics by quenching
the electric field. A high resolution ion microscope allows us to detect the
molecule's orientation and its temporal vibrational dynamics in real space. Our
study opens the door to the control of molecular dynamics in Rydberg molecules.
