  Observation of molecular dynamics with quantum state resolution is one of the
major challenges in chemical physics. Complete characterization of collision
dynamics leads to the microscopic understanding and unraveling of different
quantum phenomena such as scattering resonances. We present a new experimental
approach for observing molecular dynamics involving neutral particles and ions
that is capable in providing state-to-state mapping of the dynamics. We use
Penning ionization reaction between argon and metastable helium to generate
argon ion and ground state helium atom pairs at separation of several
angstroms. The energy of ejected electron carries the information about the
initial electronic state of an ion. The coincidence detection of ionic products
provides a state resolved description of the post-ionization ion-neutral
dynamics. We demonstrate that correlation between the electron and ion energy
spectra enables us to directly observe the spin-orbit excited Feshbach
resonance state of HeAr$^+$. We measure the lifetime of the quasi-bound
HeAr$^+$ A$_2$ state and discuss possible applications of our method.
