Vibrational excitation of ν '=1 and 2 levels of CO molecules by positron impact below the positronium formation threshold

Vibrationally inelastic (v = 0 to v-prime = 1 and 2) integral cross sections for positron-CO scattering below the positronium threshold are reported. The fixed-nuclei approximation is employed in a single-center approach. As expected, the final cross sections for the v-prime = 1 and 2 excitations are structureless with magnitudes of about (3-0.3) x 10 to the -17th/sq cm and (4-0.15) x 10 to the 20th/cu cm respectively, in the energy range from the vibrational excitation threshold up to the positronium formation threshold. The corresponding first Born results are in qualitative agreement throughout.