Knowledge Bank

The emission and absorption spectra of CaF have been examined by $Barrowandco-workers.1,2$ Their studies, as well as studies of the microwave $spectrum3$, show that the ground state is $X1\Sigma +$. There is a $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\pi -1\Sigma +$ transition near $3000\backslash AA$ and a $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\pi -1\Sigma +$ transition near $2100\backslash AA$. The present paper deals with the rotational analysis of this $C1\pi -X1\Sigma +$ system. Barrow et al obtained estimates of the upper state rotational constants from measurements of the P and Q or Q and R head separations in this system. The existence of the Q heads and the presence of $\mathrm{<mrow\; data-mjx-texclass="ORD">69</mrow>}Ga$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">71</mrow>}Ga$ in a natural abundance of 3:2 also permitted a very good vibrational analysis of the system. Our present study of the absorption spectrum yielded resolved rotational structure for the (0-0) band. The rotational constants of the $X1\Sigma +$ state were initially fixed at the values obtained by microwave $studies.2$ The resolved P and R branches were then fitted to yield constants (in $cm-1$) for $v=0$ of the $C1\Pi$ state of $\nu 00=47323,24$, $B=0.3579$, and $D=7.3\times 10-6$. Our inability to resolve the Q branch prevented us from obtaining any information regarding lambda-type doubling in the upper state. Efforts are currently being made to obtain the spectrum at somewhat higher resolution and extend the rotational analysis to other bands.