We have investigated the rotational relaxation of NH3 in NH3-He supersonic expansions by means of opto-thermal spectroscopy. Molecules are excited in the v3 + v4 band, around 5100 cm -1, using the third Stokes line of a Raman-shifted pulsed laser. Rotational distributions are measured for different values of the source stagnation pressure and NH3 concentration. At low rotational temperatures, populations deviate from a Boltzmann distribution. This is attributed to the reduction of para-to-ortho conversion during the expansion.

An Opto-Thermal Study of NH3 Rotational Relaxation in NH3-He Supersonic Expansions

Zen, Mario;Boschetti, Andrea;
1988-01-01

Abstract

We have investigated the rotational relaxation of NH3 in NH3-He supersonic expansions by means of opto-thermal spectroscopy. Molecules are excited in the v3 + v4 band, around 5100 cm -1, using the third Stokes line of a Raman-shifted pulsed laser. Rotational distributions are measured for different values of the source stagnation pressure and NH3 concentration. At low rotational temperatures, populations deviate from a Boltzmann distribution. This is attributed to the reduction of para-to-ortho conversion during the expansion.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11582/2909
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