Knowledge Bank

A new combination of transient frequency-modulation (FM) absorption and supersonioc jet expansion has been developed to study the spectroscopy of free radicals. This techniques has been successfully demonstrated in obtaining jet-cooled $A~\leftarrow X~$ spectra of $NH2$ and HCCI, In addition, a simultaneous acquisition of temporal waveform in frequency sean reveals intersting information on the velocity and density distributions of supersonic jet expansion systems. Results obtained using a pinhole nozzle and a slit nozzle show the characteristic differences between these two jet systems. The details of this technique will be presented. We have also recently used a new diode laser system to study the high resolution electronic spectroscopy of free radicals and preliminary results will be presented.