we converted the x-axis to $\mu$m in order to compare the results. The y-axis indicates the integrated intensities, given as a cross section in units of 10${^5}$ cm${^2}$ mol${^{-1}}$.

In order to explore the parts of the potential energy surface connecting the ground state geometries with those corresponding to the (5,7)-ring defected states we used the STQN method, which uses a quadratic synchronous transit approach to find the transition state and then completes the optimization using a quasi-Newton algorithm (Peng & Schlegel [@peng]; Peng et al. [@peng96]). Subsequently, we performed frequency calculations to verify that we found a transition state of first order (yielding one and only one imaginary frequency) and then the reaction path was followed by integrating the intrinsic reaction coordinate (IRC) (Fukui [@fukui]) to verify that the transition state actually connects the ground and defected states. To assess the energetics more accurately we performed these calculations using again the B3LYP functional but now in conjunction with Dunning’s cc-pVTZ basis set (Dunning [@dunning]). The energies of the ground, (5,7)-ring defected and transition states have then been calculated even more accurately using the G4(MP2) extrapolation approach (Curtiss et al. [@curtiss]) including a zero-point energy correction. These type of calculations 