ION PRODUCTION BY POSITRON-MOLECULE RESONANCES

Ion production by low-energy positrons in low-density gases was report ed by Passner, Surko, Mills, and Leventhal [Phys. Rev. A 39, 3706 (198 9)]. That work studied the ionization of hydrocarbons in a positron tr ap in the presence of a buffer ps of molecular nitrogen. We present fu rther analysis of the data from this experiment, taking into considera tion the ionization of the hydrocarbons by nitrogen ions created as a result of the positron trapping process. We conclude that ionization b y positrons was the dominant ion production mechanism at times longer than the characteristic ion confinement time of approximately 1 s, whi le ionization by nitrogen charge exchange was dominant at earlier time s. The details of the ionization spectra are also discussed.