NONDISSOCIATIVE AND DISSOCIATIVE IONIZATION OF MOLECULES BY POSITRON-IMPACT

We have performed a comprehensive experimental study of the non-dissoc iative and dissociative ionization of molecules (N-2, CO, CO2 and CH4) by positron impact [1]. Here some of the results are presented. The b ehaviour of the single, non-dissociative ionization cross sections are found to be similar to that observed previously for H-2 and noble gas targets [2]. For dissociative ionization of N-2, the positron and ele ctron impact cross sections do not merge at high velocity. This effect is similar to the well-known effect measured for example for the doub le ionization of helium.