01-044

Planetary Atmospheres

Cover Page/Proposal Summary

ROSS-00    NRA 00-OSS-01

Date Due: 4/28/2000

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Proposal Type: New Proposal

Proposal Category: Laboratory

Major Equipment Proposal? No

Do you intend to submit an Education/Public Outreach (E/PO) proposal? No

Proposal Title:
Chemical Kinetics of Planetary Free Radicals and Molecules

Abbreviated Proposal Title:
Chemical Kinetics of Planetary Free Radicals

Principal Investigator:
Dr. Louis J. Stief
Space Sciences Directorate Lab. for Extraterrestrial Physics CODE 690
NASA Goddard Space Flight Ctr.
Greenbelt, MD 20771
Phone: 301-286-7529   Fax: 301-286-1683   E-mail: louis.j.stief@gsfc.nasa.gov

SignatureDate
_________________________________________________

Co-Investigators and Collaborators:
Type    Name    Affiliation    E-mail
Sci Co-I   Dr. Walter A. Payne Jr.   NASA/GSFC   walter.a.payne@gsfc.nasa.gov
Sci Co-I   Dr. Regina J. Cody   NASA/GSFC   regina.j.cody@gsfc.nasa.gov
Sci Co-I   Dr. Paul N. Romani   NASA/GSFC   paul.n.romani@gsfc.nasa.gov
Sci Collab   Dr. Fred L. Nesbitt   Coppin State College, Baltimore, MD   fnesb29280@aol.com
Sci Collab   Dr. Dwight C. Tardy   Univ. of Iowa, Iowa City, IA   dwight-tardy@uiowa.edu


Proposal Summary:

This is a continuation proposal for research supported under RTOP # 344-33-75-04. The proposed research program will provide laboratory data on reaction rate constants as well as reaction product identities and yields needed for models of the photochemistry of the atmospheres of the outer planets and satellites. In the last three years we have completed an extensive study of the rate and products of the radical-radical reaction C2H3+CH3 at T = 298K and 200K and initiated a new study of the reaction CH3+CH3+M at temperatures appropriate for outer planet atmospheres. The latter study was prompted by the recent detection of the methyl radical CH3 in the atmospheres of both Saturn and Neptune. The levels of CH3 were much lower than predicted by atmospheric models and the observers suggested that the loss of CH3 via the self reaction CH3+CH3 was considerably underestimated based on laboratory data obtained mostly at higher temperatures and pressures. We now have data at T= 298K and 202K at P = 1 Torr He. We propose to continue this study with measurements of k (CH3+CH3) at P = 0.5 and 2.0 Torr He, T= 298K and 200K and at P = 0.5 to 2.0 Torr He, T= 160K using a newly acquired low temperature circulating pump. The T= 160K data will be very appropriate for the models of Saturn and Neptune. Some theoretical calculations will be performed to permit extrapolation of the data to the even lower pressures required for the models. Atmospheric model calculations will be performed to examine the effect of the new low pressure, low temperature lab data on the model predictions. We will initiate a study of the products of the CN+CH4 and CN+C2H6 reactions following suggestions by observers and modelers that a small yield of CH3CN from these reactions could account for the CH3CN observed in the atmosphere of Titan. There have been several direct measurements of the total rate constant over a wide temperature range but only one indirect study (at T = 298K) of the product channels.



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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:

  • certifies that the statements made in this proposal are true and complete to the best of his/her knowledge;
  • agrees to accept the obligations to comply with NASA award terms and conditions if an award is made as a result of this proposal; and
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