PERIODIC-ORBITS AS A PROBE TO REVEAL EXOTIC STATES IN VIBRATIONALLY EXCITED MOLECULES - THE SADDLE-NODE STATES

We present theoretical results which show the existence of isomerizing localized quantum states above potential barriers for the excited B-1 (2) of SO2 and O3. These states are assigned by periodic orbits which emerge from saddle-node bifurcations, the characteristic of which is t he simultaneous generation of two families of periodic orbits one stab le and one unstable. Similar isomerizing states and bifurcations have been found for other molecules, and this leads to the conclusion, that the appearance of saddle-node type states may be a generic phenomenon for molecular potentials with barriers.