Other
Scientific paper
Nov 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001dps....33.2208c&link_type=abstract
American Astronomical Society, DPS Meeting #33, #22.08; Bulletin of the American Astronomical Society, Vol. 33, p.1080
Other
1
Scientific paper
The methyl free radical (CH3) has been observed in the atmospheres of Saturn, Neptune and recently by Cassini - CIRS in Jupiter. Atmospheric models predict much higher abundances of CH3 than observed, especially in the case of Saturn. A major, but not exclusive, cause of the disagreement has been identified as the underestimation of the loss process for CH3 via the self-reaction at the low temperatures and pressures prevailing in these atmospheric systems. Although the reaction CH3 + CH3 + M -> C2H6 + M has been extensively studied both theoretically and experimentally, the laboratory conditions have been, with only a few exceptions, higher temperatures and pressures than those present in the outer planet atmospheres or M=Ar rather than H2 or He as the bath gas. We are measuring the rate constant of this reaction under physical conditions more suitable to these atmospheres, i.e. P = 0.6-2.0 Torr of He and T < 298K. Our measurements are now extended to T = 155K. The experimental technique is discharge fast flow with mass spectrometric detection and monitoring of the CH3 decay. The methyl radical is generated via the fast reaction F + CH4 -> CH3 + HF. The lowest temperature of our or any other previous research was T = 200K. To work at lower temperatures required a new flow tube design and a different cooling technique. Both of these changes were made successfully. The experimental results at T = 155K and P = 0.6-1.5 Torr He will be presented. The results are shown to be invariant for CH3 concentrations in the range (4.5-10.8)x1012 radicals cm-3. The impact of these results upon photochemical models of planetary atmospheres will be discussed in the paper by P. Romani and D. Tardy to be presented at this meeting. The Planetary Atmospheres Program of NASA Headquarters has provided the funding for this research.
Cody Regina J.
Iannone Mark A.
Nesbitt Fred L.
Stief Louis J.
No associations
LandOfFree
Rate Constant for the CH3 Recombination Reaction at T = 155K: A Loss Process in Outer Planet Atmospheres does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Rate Constant for the CH3 Recombination Reaction at T = 155K: A Loss Process in Outer Planet Atmospheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rate Constant for the CH3 Recombination Reaction at T = 155K: A Loss Process in Outer Planet Atmospheres will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1237900