Temperature Dependent Studies of Ion Lifetimes

The lifetimes of SF$_{6}^{-}$ ions produced in K(np)/ SF$_{6}$ collisions at high n , n$\ge $ 30 are being investigated over a temperature range of 300K $\sim $600K. At room temperature, it is observed that collisions lead predominantly to the formation of long-lived ($\tau \ge $ 1ms) SF$_{6}^{-}$ ions. The mean ion lifetime, however, decreases as the target gas temperature is increased and the data provide evidence of creation of short-lived ions having a range of lifetimes that extends below one microsecond. Such behavior is consistent with simple statistical theory. Limited SF$_{5}^{-}$ production is also observed at the higher temperatures. Measurements are being extended to a range of other attaching targets to further examine the role of internal energy in governing electron capture processes.