NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Measurements of the methane relaxation times for application to the infrared emission models of the upper atmospheres of outer planets and TitanThe 7.8 micrometer emission from the nu(sub 4) band of methane (CH4) is a regularly observed feature in the stratosphere of all the giant planets and Titan. On Jupiter, enhancements in this emission are associated with the infrared hot spots in the auroral zone. Attempts to model this phenomenon in particular, and to understand the role of methane in general, have been hampered in part by a lack of adequate laboratory measurements of the collisional relaxation times for the nu(sub 3) and nu(sub 4) levels over the appropriate temperature range. To provide this needed data, a series of laboratory experiments were initiated. In the experimental arrangement the nu(sub3) band of methane is pumped at 3.3 micrometers using a pulsed infrared source (Nd:YAG/dye laser system equipped with a wave-length extender). The radiative lifetime of the nu(sub 3) level (approximately 37 ms) is much shorter than the nu(sub 4) lifetime (approximately 390 ms); however, a rapid V-V energy transfer rate ensures that the nu(sub 4) level is substantially populated. The photoacoustic technique is used to acquire relaxation rate information. The experiments are performed using a low-temperature, low-pressure cell. Experimental apparatus and technique are described. In addition some of the experimental difficulties associated with making these measurements are discussed and some preliminary results are presented.
Document ID
19900017443
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Halthore, Rangasayi N.
(Applied Research Corp. Landover, MD., United States)
Caldwell, John J.
(Institute for Space and Terrestrial Science Concord (Ontario)., United States)
Allen, John E., Jr.
(NASA Goddard Space Flight Center Greenbelt, MD., United States)
Burt, Jim A.
(York Univ. (England). Downsview, Ontario , Canada)
Yang, Kuanghua
(York Univ. (England).)
Delaney, Paul
(York Univ.)
Date Acquired
August 14, 2013
Publication Date
May 1, 1990
Publication Information
Publication: First International Conference on Laboratory Research for Planetary Atmospheres
Subject Category
Lunar And Planetary Exploration
Accession Number
90N26759
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
No Preview Available