Knowledge Bank

Excitation spectra of the CaF $A2\Pi -X2\Sigma$(0,0), (1,1), and (1,0) bands have been observed and assigned. The rotational analysis of the CaF $A-X$ and $B-X$ bands by B. S. Mohanty and K. N. Upadhya [Ind. J. Pure Appl. Phys. 5, 523 (1967)] is shown to be incorrect. Because it is possible to make independent rotational assignments of each line in an excitation spectrum by observing frequency differences and relative intensities in photoluminescence spectra, tunable laser excitation spectroscopy promises much less ambiguity than traditional techniques for assignment of dense, badly overlapped spectra. The following spectroscopic constants (in $cm-1$) are obtained for the CaF $A2\Pi$ and $X2\Sigma$ states. Numbers in parentheses correspond to three standard deviations uncertainty in the last digit. \def \a {\hphantom{$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2$}} [FIGURE] The origin of the $A2\Pi 1/2-X2\Sigma$ (1,1) subband lies 5.62(30) $cm-1$ to the blue of the corresponding (0,0) subband origin. The (0,0) band $Q2$ head is observed to form at J = 26 $\pm$ 0.5. The difference of the $A2\Pi$ effective rotational constants is $2B2/A$. The $A2\Pi$ lamba doubling constant, p, agrees well with the pure precession estimate of the interaction between the $A2\Pi$ and $B2\Sigma$ states.