Session J15 - Poster Session II.
POSTER session, Sunday morning, April 20
Congressional Hall, Renaissance
A cylindrical radio-frequency ion trap(Located at the Harvard-Smithsonian Center for Astrophysics) was prepared to store a population of O_2^+ ions in an effort to observe the fluorescence decay of the a^4\Pi _u metastable state of O_2^+.(This work supported in part by Research Corp. Grant No. CC4323.) A metastable O_2^+ ion population was produced inside the cylindrical rf trap by electron bombardment of O_2 at pressures ranging from 4~to~8\times 10^-8~Torr. After the ions were created, the radiative decay of the population was monitored versus time by focusing a fraction of the light emitted by the decaying metastable ions onto a narrow-band (\Delta \lambda \leq 10~nm) interference filter in front of a photomultiplier tube operated in a photon-counting mode. Two different interference filters were used: peak transmittances were at 235- and 265-nm, respectively. Fluorescence decay curves resulted at all pressures and with either interference filter, as long as the trap was tuned for O_2^+ storage. The decay curves indicate at least two primary decay channels exist for the decaying population. This observation corroborates a preliminary report that monitored the fluorescence decay of an O_2^+(a^4\Pi _u) population confined to a Kingdon trap, and also, one of several published lifetime measurements, which did not employ the observation of fluorescence decay.