The results section is divided into four main subcategories. The first section is focused on the ground state thermodynamic properties. Before computing the thermochemical properties and spectral features of the test molecules, C 4 and C 4 H, a validation study is done to compare the results with those available in the literature. The molecules used in the validation study are mainly smaller carbon clusters and hydrocarbons. We next discuss the effects of low lying electronic states on the thermochemistry since the low lying states become important in the high temperature regime corresponding to the boundary layer during hypersonic reentry.