INTRACAVITY LASER-ABSORPTION SPECTROSCOPY OF NO2 AND CH4 COOLED IN A SLIT JET SUPERSONIC EXPANSION

The intracavity Laser Absorption Spectroscopy (ICLAS) has been use to observe weak absorption of NO2 and CH4 cooled in a supersonic jet through a slit. By this method, the thermally congested spectrum of the molecules is drastically simplified and analysis becomes possible. On NO2 we report preliminary results in the 13 470 - 14 440 cm-1 energy range where 20 vibronic bands have been observed. On CH4 the V(CH) = 5 overtone centered at 13 750 cm-1, which is unresolved at room temperature, displays only few lines not yet analysed.