Cover Page/Proposal Summary

ROSS-00    NRA 00-OSS-01

Date Due: 4/28/2000

SRI International proposes a laboratory experimental study to identify the products created in dissociative recombination of O2+ and CO2+ with electrons. Reactions of this nature are of critical importance in modeling the atmospheres of Mars and Venus. While the total rate constants for such reactions have long been known, the proposed work represents the first attempt to directly establish the products of recombination of CO2+ and the dependence of the recombination rate and product yields on the extent of vibrational excitation in O2+. The dissociative recombination measurements will be made at the CRYRING molecular-ion storage ring facility using ion sources characterized at SRI. Excited vibrational levels of O2+ are predicted to be significantly populated in the upper ionospheres of Mars and Venus. Theory indicates that product yields are dominated by the energetic accessibility of potential curve crossings between the ground state of the ion and repulsive states leading to the fragment atoms. The presence of vibrational excitation is likely to change the branching ratios for production of specific atomic states, which are otherwise known only for the ground vibrational level of O2+. The only information available on the products of dissociative recombination of CO2 comes from laboratory experiments on emissions from excited CO, which are difficult to interpret quantitatively. Sufficient energy is available to produce CO(a), O(1D,1S), and even C + O2. The proposed experiments will measure the translational energy imparted to the neutral fragments and infer the branching between the energetically allowed channels. The results of the proposed work will be used by modelers to understand optical emissions, atmospheric heating, and planetary escape.

Certification of Compliance with Applicable Executive Orders and U.S. Code

By submitting the proposal identified in this Cover Sheet/Proposal Summary in response to this NRA or AO, the Authorizing Official of the proposing institution (or the individual proposer if there is no proposing institution) as identified below: