Interaction of electrons with CO2 van der Waals clusters

Molecular-beam measurements are reported for the ionization and electron attachment cross sections sigma-bar/sub +/(N-bar, E/sub e/) and sigma-bar/sub -/(N-bar, E/sub e/) for CO2 van der Waals clusters. The cross sections were measured as a function of the mean cluster size N for electron energies 1 less than or equal to E/sub e/ less than or equal to 200 eV and were found to increase with N-bar for N-bar less than or equal to (1--3) x 103. The maximum in sigma-bar/sub +/(E/sub e/) shifted toward higher E/sub e/ as N-bar increased, while the dependence sigma-bar/sub -/(E/sub e/) was more complicated. In particular, sigma-bar/sub -/(E/sub e/) had a peak at E/sub e/ approx. = 2 eV, which indicates that CO2- ions were formed in the clusters. The retarding potential method was used to find the size distribution of the charged and neutral clusters. The distributions show the effects of cluster vaporization and fragmentation during ionization and demonstrate that multiply charged ions were formed