LINE-SHAPE ANALYSIS OF DOPPLER-BROADENED FREQUENCY-MODULATED LINE SPECTRA

We present a method for recovering Doppler broadened absorption line s hapes from frequency modulated (FM) line spectra. The method of analys is is calibrated and demonstrated with thermalized CN radicals produce d by photodissociation of cyanogen (NCCN), probed on the A-X system ne ar 800 nm with a frequency modulated Ti: sapphire ring laser. Nontherm al, Doppler broadened lines from translationally nascent photofragment s can also be recovered by direct transformations of experimental FM l ine profiles acquired with a time resolution exceeding 100 ns. The sup erior signal-to-noise afforded by FM spectroscopy, relative to other d irect absorption methods, should encourage the application of transien t FM spectroscopy to problems in photoinitiated reaction dynamics. (C) 1996 American Institute of Physics.