Excitation of the nitro group in nitromethane by electron transfer

In this paper we report on complementary measurements on ion-pair formation in collisions between K atoms and CH₃NO₂ molecules. The experiments were performed in a c.m. energy range from 20 up to 300 eV. Double differential cross sections were obtained by measuring the K⁺ ion yield as a function of the scatter angle and as a function of the post-collision laboratory energy. On the other hand, relative total partial cross sections for the formation of CH₃NO^- ₂, NO^- ₂, and O^- were measured in the same energy range. The experimental results lead to the conclusion that in this energy range electron transfer takes place to three ionic states of CH₃NO^- ₂, a dominantly repulsive ²A₁ state and two ²B₁ states with relatively deep potential wells.