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The rate parameters for coupled vibration-dissociation in a generalized SSH approximationA theoretical study of vibrational excitations and dissociations of nitrogen undergoing a nonequilibrium relaxation process upon heating and cooling is reported. The rate coefficients for collisional induced vibrational transitions and transitions from a bound vibrational state into a dissociative state have been calculated using an extension of the theory originally proposed by Schwarz (SSH) et al. (1952). High-lying vibrational states and dissociative states were explicitly included but rotational energy transfer was neglected. The transition probabilities calculated from the SSH theory were fed into the master equation, which was integrated numerically to determine the population distribution of the vibrational states as well as bulk thermodynamic properties. The results show that: (1) the transition rates have a minimum near the middle of the bound vibrational levels, causing a bottleneck in the vibrational relaxation and dissociation rates; (2) high vibrational states are always in equilibrium with the dissociative state; (3) for the heating case, only the low vibrational states relax according to the Landau-Teller theory; (4) for the cooling case, vibrational relaxation cannot be described by a rate equation; (5) Park's (1985, 1988) two-temperature model is approximately valid; and (6) the average vibrational energy removed in dissociation is about 30 percent of the dissociation energy.
Document ID
19880059848
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Sharma, Surendra P.
(NASA Ames Research Center Moffett Field, CA, United States)
Huo, Winifred M.
(NASA Ames Research Center Moffett Field, CA, United States)
Park, Chul
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 13, 2013
Publication Date
June 1, 1988
Subject Category
Inorganic And Physical Chemistry
Report/Patent Number
AIAA PAPER 88-2714
Accession Number
88A47075
Distribution Limits
Public
Copyright
Other

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