The energy dependence of some neon-ion-neutral reaction rate coefficients investigated in a flow-drift tube experiment

A new flow-drift apparatus is described in which gas phase ion mobilities and reaction rate coefficients may be determined over an ion energy range extending from thermal energy at 300K to several eV. Rate coefficients for the reactions of Ne + with H 2 S, SO 2 , CO 2 , NH 3 , N 2 and CO have been obtained as a function of ion-neutral relative kinetic energy E CM . Measurements of the mobility of Ne + in helium and of the He + +N 2 reaction rate coefficient are compared with existing experimental data. The six neon ion reaction rate coefficient are compared with existing experimental data. The six neon ion reactions studied exhibit three distinctive forms of energy dependence; large rate coefficients weakly dependent on E cm (SO 2 , H 2 S); rate coefficients showing pronounced minima as E CM is varied (CO 2 , NH 3 ), and rate coefficients increasing by several orders of magnitude as E CM is increased (N 2 , CO). These energy dependences are discussed in terms of simple models for the interactions.