Rydberg States of CaCl Observed by Optical-Optical Double Resonance

Abstract

We have observed s, p, and d Rydberg series of CaF in the region from 40,600 to 45,905 and have recently begun work on the Rydberg series of CaCl. We scanned the region from $40,898 cm^{-1}$ to $41,860 cm^{-1}$ and observed only one $^{2}\Sigma$ state at $41.260 cm^{-1}$. Pulsed-pulsed optical-optical double resonance via the intermediate $B{^{2}}\Sigma^{+}$ state is used to excite the Rydberg states. OODR transitions are detected by observation of direct UV fluorescence. The fluorescence from this state is weak compared with that typically observed for CaF. Its lifetime appears to be much shorter than those we have observed for CaF Rydberg states. We have also examined the region from $43,527 cm^{-1}$ to $45,431 cm^{-1}$ and found no states in this region. We also expected to see more states in the lower energy region where we found one $^{2}\Sigma$ state. Since both regions examined are above the dissociation limit $(32,988 cm^{-1})$, the absence of states could be explained by predissociation. The characteristics of the observed $^{2}\Sigma$ state also suggest prcdissociation. Future plans include detection of OODR by the fluorescence dip method used previously for CaF.