SPECTROSCOPY AND NONEQUILIBRIUM DISTRIBUTION OF VIBRATIONALLY EXCITEDMETHANE IN A SUPERSONIC JET

High-resolution spectra of supersonic jets of vibrationally excited me thane have been recorded by diode laser in the 8 mu m region. A formal ism for the description of energy distribution is proposed. It allows to estimate populations of vibrational polyads. Under these non-equili brium conditions, translational temperature is also measured from line profiles. For relaxation, it is shown that vibrational relaxation bet ween polyads is negligible whereas strong redistribution of population arises inside each polyad. Spectroscopically, observed lines involvin g the first four excited polyads allows cross-checked tests for energy level analysis. (C) 1998 Elsevier Science Ltd. All rights reserved.