  We report an analysis of intramolecular dynamics of the highly excited planar
carbonyl sulfide (OCS) below and at the dissociation threshold by the Fast
Lyapunov Indicator (FLI) method. By mapping out the variety of dynamical
regimes in the phase space of this molecule, we obtain the degree of regularity
of the system versus its energy. We combine this stability analysis with a
periodic orbit search, which yields a family of elliptic periodic orbits in the
regular part of phase space an a family of in-phase collinear hyperbolic orbits
associated with the chaotic regime.
