Because the reaction is in the inverted regime, for which τ < 0, the product trajectory travels backwards in imaginary time. This implies that the corresponding action, S g , is negative due to the order of the integration limits in Eq. (2b) and therefore contributes to a reduction of the total action, S. This is the reason that tunneling effects are typically stronger in the inverted regime than the normal regime. In analogy to the Feynman-Stückelberg interpretation of particle physics, in which particles traveling backwards in time are identified with antiparticles traveling forwards in time, instanton theory suggests a very interesting interpretation for the reaction mechanism in thiophosgene. Reading Fig. chronologically from left to right, we start out with an ordinary molecule on the reactant surface. After some time of propagation, a molecule-anti-molecule pair is created at the hopping point, the former traveling on the reactant surface, the latter traveling on the product surface. At the end of the anti-molecule's trajectory it meets the original molecule at the hopping point where they annihilate leaving only the newly created molecule on the reactant surface which restarts the periodic cycle.