Collisions of low-energy electrons with CO2

We report cross sections for collisions of low-energy electrons with carbon dioxide obtained by the Schwinger multichannel variational method. Elastic cross sections are obtained in the static-exchange-plus-polarization approximation. We pay particular attention to the position of the (2)Pi(u) resonance and to the strong enhancement in the integral cross section near zero energy, both prominent features whose accurate treatment requires an accounting for polarization effects. To include such effects in the resonant symmetry, we use an objective and physically motivated criterion to construct a set of configurations that accurately accounts for polarization while avoiding overcorrelation. In addition, we study the origin of the nonisotropic behavior of the elastic differential cross section at very low energies and conclude that it is caused by significant contributions from vibrationally excited CO2. Cross sections from threshold to 50 eV for excitation of the (3)Sigma(u)(+), (1)Delta(u), (3)Delta(u), (3)Sigma(u)(-), and (1)Sigma(u)(-) states that arise from the (1 pi(g)--> 2 pi(u)) transition are presented for the first time. (C) 1999 American Institute of Physics. [S0021- 9606(99)01633-5].