Negative ion formation in potassium–nitromethane collisions

Ion-pair formation in gaseous nitromethane (CH3NO2) induced by electron transfer has been studied by investigating the products of collisions between fast potassium atoms and nitromethane molecules using a crossed molecular-beam technique. The negative ions formed in such collisions were analysed using time-of-flight mass spectroscopy. The six most dominant product anions are NO2−, O−, CH3NO2−, OH−, CH2NO2− and CNO−. By using nitromethane-d3 (CD3NO2), we found that previous mass 17 amu assignment to O− delayed fragment, is in the present experiment may be unambiguously assigned to OH−. The formation of CH2NO2− may be explained in terms of dissociative electron attachment to highly vibrationally excited molecules.