Knowledge Bank

We have combined the high sensitivity of the Intracavity Laser Absorption Spectroscopy (ICLAS) with the rotational cooling of a jet expansion. By inserting a 24 cm long slit jet or a series of 78 pinholes jet in a dye or Ti:Sapphire laser cavity, an equivalent pathlength of more than 10 km through rotationally cooled molecules has been achieved. By this way the thermally congested overtone spectra of molecules such as $CH4(\Delta \nu CH=4and5)$ have been drastically simplified and some rotational assignment become possible. Some other examples will be given.