Observation of multiple ionization pathways for OCS in an intense laser field resolved by three-dimensional covariance mapping and visualized by hierarchical ionization topology

The two- and three-body Coulomb explosion of carbonyl sulfide (OCS) by 790nm, 50 fs laser pulses focussed to $\approx $ 10$^{16}$ Wcm$^{-2}$ has beeninvestigated by three-dimensional covariance mapping technique. For the firsttime in a triatomic molecule, a single charge state, in this case thetrication, has been observed to dissociate into two distinct energy channels.With the aid of a three dimensional visualization technique to reveal theionization hierarchy, evidence is presented for the existence of two sets ofionization pathways resulting from these two initial states. While one group ofions can be modeled using a Classical enhanced ionization model, the secondgroup, consisting of mainly asymmetric channels, can not. The results provideclear evidence that an enhanced ionization approach must also be accompanied byan appreciation of the effects of excited ionic states and multi-electronicprocesses.Comment: 12 pages, 9 figures, accepted for publication in Phys. Rev. A, reference to follo