Theoretical Studies in Aeronomy

Institute For Scientific Research Inc, Winchester MA

Investigators

Abstract

Electron-ion collisions play an important role in determining the plasma and chemical properties of the Earth's ionosphere. Using parameters calculated under prior National Science Foundation support, theoretical quantal calculations will be made to determine the atomic state quantum yields resulting from the dissociative recombination of N2+ with an electron, i.e. N2+ + e- leading to N + N. Dissociative recombination generates the N(2D) and N(2P) excited states, upper states of well known ionosphere emission lines. Vibrationally excited ions are present at high abundance in the ionosphere but atomic quantum yields for excited ions have never been determined by theory or experiment. By using a new technique, the project will yield accurate quantum yields for the lowest five ion vibrational levels over the wide range of ionospheric electron temperatures. Calculations will also be performed for the vibrational deexcitation of N2+ by electrons, and for the rotational deexcitation and excitation of N2+ by electrons in the Earth's ionosphere. These processes may have high rate constants. Currently, there is no theoretical or experimental information on this fundamental process. Calculations will also be performed for another molecular species in the ionosphere, NO+, since recent observations found that highly rotationally excited NO+ is present in the upper atmosphere. None of the prior laboratory experiments or theoretical calculations have determined dissociative recombination rate constants and quantum yields for very high rotationally excited NO+. Using techniques similar to those developed for the study of N2+, the dissociative recombination rate constants and quantum yields will be determined for NO+ with high rotational excitation. For relaxed ions, prior experimental studies have disagreed on the electron temperature dependence of the dissociative recombination rate constant. The electron temperature dependence and the quantum yields will be calculated for the full range of ionospheric temperatures. The broader impacts of the project include the convening of an international conference devoted to the latest developments in dissociative recombination research. The 8th Meeting will be held in 2010 at Lake Tahoe, California, with the project providing support for student travel. A website on dissociative recombination is maintained, which provides the rate coefficient data for N2+ for dissociative recombination, vibrational excitation/relaxation and rotational excitation/relaxation and the full set of data that enters the calculations. A section of the website is allotted to explanatory material and an animation for nonexperts.