Knowledge Bank

Ab-initio SCF + CI calculations of the structure and properties of $C2$ and $C3$ are described. The calculations on $C2$ utilized a large Slater basis, while those on $C3$ used a double-zeta-plus-polarization Cartesian Gaussian basis set. Large scale CI calculations (10 000 to 15 000 spin-adapted configurations) were performed on the low-tying states of $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma g+$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi g,u$ symmetries for $C2$ and for the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma g+$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\pi g,u$ symmetries for $C3$. The sum of the squares of the electronic transition moments, $\Sigma |Re|2$, between the various states as a function of internuclear distance are reported. The application of these results to entry physics studies being conducted at NASA-Ames Research Center are also described.