State-to-state vibrational and rotational energy transfer in CO2 gas from time-resolved raman–infrared double resonance experiments
✍ Scribed by G. Millot; C. Roche
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 381 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
A time-resolved Raman-infrared double resonance technique was used to study collisional relaxation rates of vibrational and rotational energy levels in gas at 295 K. A pulsed Raman excitation populated a selected CO 2 rovibrational initial state. Measurements of the rates of transfer from the pumped initial state into speciÐc Ðnal states were carried out using time-resolved laser absorption spectroscopy. First, the transfer rates were determined for the Ðve lower vibrational energy levels. In particular, it was conÐrmed that the rate of transfer between the two Fermi levels ( 1000) and ( 0200) is very small [ (5.3 » 0.2) Â 104 Torr-1 s-1 ] . The rotational structure inside the (0200) vibrational level was also studied. A kinetic master equation was used to model energy transfer among rotational levels. The state-to-state rotational energy transfer rates were calculated by the Ðtting and scaling laws. The ability of di †erent laws (ECS-P, ECS-EP, MEG) was then compared in order to reproduce the timedependent population evolution.