THE CaO $c^{3}\Sigma^{+} - a^{3}\Pi$ SYSTEM

A portion of the CaO ``Second Orange Are Band System’’ (617-627nm) has been assigned as the 0,0 band of the $c^{3}\\Sigma^{+}-a^{3} \\Pi$ transition. $c^{3} \\Sigma^{+}$ is derived from a $x^{3} x^{i}$ configuration and is isoconfigurational with the recently observed D,$d^{1},^{3}\\bigtriangleup$ $state.^{1}$ Sub-Doppler spectroscopy is required to resolve the dense rotational structure. Intermodulation spectroscopy has been employed. The band system has been observed in a $Ca + O_{3}$ flame. It originates in the same lower electronic and vibrational states as another prominent CaO band system recently observed in a $Ca + N_{2}O + CO$ flame. However, no part of the ``Second Orange Are Band System’’ has been observed following the latter reaction. This investigation has yielded $B_{O}(c^{3} \\Sigma +) = 0.350 cm^{-1}$ and $R_{Q23}(1) = 16165.7 cm^{-1}$. The latter value compares favorably with that predicated by Bauschlicher and Yarkony$(16500 cm^{-1})^{2}$ for the location of $c^{3}\\Sigma^{+}$ relative to $a^{3}\\Pi$. $^{1}$ R.F Marks, H.S. Schweda, R.A. Gottscho, and R.W. Field, J. Chem. Phys. 76, 4689 (1982). $^{2}$ C.W. Bauschlicher, JR. and D.R. Yarkony, J. Chem. Phys. 68, 3990 (1978).