Formation of negative hydrogen ions in 7-keV OH+ + Ar and OH+ + acetone collisions: a general process for H-bearing molecular species

We demonstrate that the formation of negative hydrogen ions (H${}^{\ensuremath{-}}$) occurs in a wide class of atomic and molecular collisions. In our experiments, H${}^{\ensuremath{-}}$ emission from hydroxyl cations and acetone molecules was observed in keV-energy collisions. We show that hydride (H${}^{\ensuremath{-}}$) anions are formed via direct collisional fragmentation of molecules, followed by electron grabbing by fast hydrogen fragments. Such general mechanism in hydrogen-containing molecules may significantly influence reaction networks in planetary atmospheres and astrophysical media and new reaction pathways may have to be added in radiolysis studies.