Ion Decay Studies in Photo-Ionized Bromine
Abstract
The loss processes of ions observed in photo-ionized Br2 have been studied by determining the time dependence of the ion number densities in the afterglow using quadrupole mass analysis techniques. The most abundant initially observed negative ion was Br-. This species was found to convert to Br3- in the afterglow by the three-body reaction Br-+2Br2--> Br3- +Br2. The coefficient for the process was found to be kc=2.9×10-29 cm6/sec at 296 °K. The negative-ion-positive-ion ambipolar diffusion coefficients (Da-p) for Br- and Br3- were found to be 12.9 and 7.5 cm2 Torr/sec, respectively. The Br3- species was found to decay mainly by ion ambipolar diffusion. The positive-ion species Br+, Br2+, and Br3+ were observed in the afterglow. Of these, the Br2+ ion was initially most abundant. Although a rapid reaction involving Br+ takes place in the early afterglow, Br2+ and Br3+ decay mainly by diffusion. Da+p for the Br2+ was determined to be 12.6 cm2 Torr/sec for the case where the electron number density has decayed to zero and the predominant negative ion was Br-. The ambipolar diffusion coefficient for Br3+ was found to be essentially identical to that for the Br3- ion under the conditions where the Br3+ ion and Br3- ion were the predominant ion species present.
- Publication:
-
Physical Review A
- Pub Date:
- July 1971
- DOI:
- 10.1103/PhysRevA.4.114
- Bibcode:
- 1971PhRvA...4..114T