ANALYSIS OF $^{3}\Delta - ^{3}\Pi$ TRANSITIONS IN THE ORANGE SYSTEM OF CaO BY INTERMODULATION SPECTROSCOPY

Author Institution:In the orange bands of Cao numerous overlapped rotational progressions result in complicated spectra which are largely unassignable by traditional methods due to Doppler-limited resolution. Using the technique of intermodulation spectroscopy dense spectra ($\sim 40$ lines per $cm^{-1}$) are easily resolved. The output of a single mode cw dye laser is split into two beams which are independently chopped and counterpropagated through a $Ca + N_{2}O + $CO low pressure flame. The sub-Doppler excitation features (typically 100 MHz fwhm) are recovered using two lock-in amplifiers in series. Unambiguous rotational assignment is quickly obtained by detecting resolved fluorescence using an optical multichannel analyzer. Fluorescence data are also used to assign relative parity of lambda doublets in $a^{3}\Pi$ as well as $\Omega^{\prime\prime}$