  The two- and three-body Coulomb explosion of carbonyl sulfide (OCS) by 790
nm, 50 fs laser pulses focussed to $\approx $ 10$^{16}$ Wcm$^{-2}$ has been
investigated by three-dimensional covariance mapping technique. For the first
time in a triatomic molecule, a single charge state, in this case the
trication, has been observed to dissociate into two distinct energy channels.
With the aid of a three dimensional visualization technique to reveal the
ionization hierarchy, evidence is presented for the existence of two sets of
ionization pathways resulting from these two initial states. While one group of
ions can be modeled using a Classical enhanced ionization model, the second
group, consisting of mainly asymmetric channels, can not. The results provide
clear evidence that an enhanced ionization approach must also be accompanied by
an appreciation of the effects of excited ionic states and multi-electronic
processes.
