These four parameters (g, h, s x , s y ) are employed to characterize the topography of the double cone to first order. However, these parameters alone do not provide an obvious connection to the coupled electronic and nuclear dynamics that may result via passage through this region of the PES. Recent work by Lindh et al. resulted in the definition of composite parameters that correlate to possible reactive outcomes following passage through the region of the CI. The authors defined the following two parameters: