Vibrational excitation of acetylene by positron impact

Vibrationally inelastic quantum calculations are carried out at low collision energies for the scattering of a beam of positrons off acetylene gaseous molecules. The normal mode analysis is assumed to be valid and the relative fluxes into the C–C and C–H symmetric vibrational modes are computed within a Body-Fixed (BF) formulation of the dynamics by solving the relevant vibrational Coupled Channels (VCC) equations. The clear dominance of the C–C mode is observed near threshold and the implications of this finding are briefly considered in relation to more global indicators like the average vibrational energy transfer indices as obtained in the present work.