THE PREDISSOCIATION MECHANISM FOR ${^{2}}\Sigma^{+}$ RYDBERG STATES OF CALCIUM MONOCHLORIDE

Author Institution: Department of Chemistry, Massachusetts Institute of Technology; Department of Chemistry, Tsinghua UniversityThis talk summarizes experimental results from recent ion-dip spectroscopy studies of CaCl as well as previously unpublished optical-optical-double-resonance work with specific regard to predissociation processes of $^{2}\Sigma^{+}$ Rydberg states in the low-$n^{\ast} (n^{\ast} < 7, IP-E \sim 2500 cm^{-1})$ region. A single repulsive state (assigned as ${^{2}}\Sigma^{+}$) was found to be responsible for all observed predissociations of $^{2}\Sigma^{+}$ Rydberg states. The $n^{\ast}$-dependent internuclear distances of the intersections between Rydberg and repulsive $^{2}\Sigma^{+}$ states were determined through the use of trial-and-error Franck-Condon calculations. Values of the $n^{\ast}$-scaled electronic matrix elements governing the Rydberg $\leftrightarrow$ repulsive state interaction were obtained from the measured linewidths $(.6 < \Gamma < 1.2 cm^{-1})$ and computed Franck-Condon densities. With the assumption of a one-parameter form for the repulsive curve. $E(cm^{-1})=\frac{C_{***}}{R^{***}}+D_{e},$ where $C_{12}$ has the units ${\AA} {^{12}}cm^{-1}$ and $D_{e} = 33171 cm^{-1}$ for CaCl, the optimum values of $C_{12}$ was found to be $2.354 \times 10^{8} {\AA} {^{12}}cm^{-1}$