State-resolved collision energy dependence of Penning ionization cross sections for N2 and CO2 by He*23S

The state-resolved collision-energy dependences of Penning ionization cross sections σ(E) were measured in an energy range (60<E<400 meV) for N2 and CO2 with He*23S by using a very high-intensity He* beam (1.8×1015 s−1 sr−1) and detecting energy-analyzed electrons as functions of time-of-flight of He*. The partial ionization cross sections for Π states (N+2B:A2Πu, CO+2B:X2Πg, A2Πu) were observed to increase more rapidly with the increase of the collision energy than those for Σ states (N+2B:X2Σ+g, B2Σ+u, CO+2B:B2Σ+u,C2Σ+g). In the studied energy range, the repulsive walls for end-on collisions were indicated to be harder than those for side-on collisions. The directional peculiarity of the potential surfaces was related to the anisotropy in the hybridization of He* orbitals interacting with the target molecules.