HIGH RESOLUTION, ROTATIONALLY RESOLVED ELECTRONIC SPECTRA OF $CaC_{5}H_{5}$.

$^{1}$E.S.J. Robles, A. M. Ellis and T.A Miller, J. Am. Chem. Soc. 114, 7171 (1992). $^{2}$L.C. O’Brien and P.F. Bernath, J. Am. Chem. Soc. 108, 5017 (1986).Author Institution: Department of Chemistry, Laser Spectroscopy Facility, The Ohio State universityHigh resolution, rotationally resolved spectra have been acquired and analyzed for both spin orbit components of the $0^{0}_{0}$ and $4^{1}_{0}$ bands in the $\bar A^{2}E \leftarrow \bar X^{2} A_{1}$ transition of $CaC_{5}H_{5}$. The free radical $CaC_{5}H_{5}$ was generated by laser ablation of a Ca rod in a supersonic free jet expansion seeded with cyclopentadiene. Analysis is consistent with the proposed $C_{5v}$ geometry of a Ca atom centered over the $C_{5}H_{5}$$ring.^{1,2}$ The fitted rotational constants can be used to estimate the $Ca/C_{5}H_{5}$ distance to be 2.33 {\AA} in the ground state. The excited State $Ca/C_{5}H_{5}$ distance shortens by .060 {\AA} as suggested by earlier Franck-Condon $analysis.^{1}$ The electronic orbital angular momentum is largely unquenched and no Jahn-Teller activity could be measured. Details of the analysis, interpretation of the fitted constants and their implications for other metal-cyclopentadienly1 such as $MgC_{5}H_{5}$ will be presented