The CaCCH A(2)Pi-X-2 Sigma(+) 5(2)(2) and 5(2)(0) bands studied by high resolution spectroscopy: The Ca-C-C bending vibration and vibronic interaction

The CaCCH 5(2)(2) and 5(2)(0) bands in the (A) over tilde(2) Pi-(X) over tilde(2) Sigma(+) system, involving the excited Ca-C-C bending vibrations, have been rotationally analyzed via CW dye laser excitation and dispersed fluorescence with a CCD array detector. The (A) over tilde(2) Pi upsilon(5) = 2 level is subject to Renner-Teller and spin-orbit splittings; in addition, K-resonance interactions are observed between the nearby (2) Phi and (2) Pi vibronic components. With a full matrix treatment of the six vibronic components (kappa(2) Pi, mu(2) Pi and (2) Phi) in the upper state, the line positions of the six subbands of the 5(2)(2) band were fitted simultaneously by least squares. The three higher vibronic components, especially the kappa(2) Pi(1/2) component, were found to be perturbed strongly by the lower vibronic components of the upsilon(5)((2)) = 3 level. This perturbation has been analyzed by means of second-order perturbation theory involving the (B) over tilde(2) Sigma(+) electronic state and results in an estimate of the dipolar vibronic interaction parameter, epsilon(5)((2))omega(5) = -8.31 cm(-1). The 5(2)(0) band was studied through dispersal fluorescence and served to establish an accurate energy of the upsilon(5) = 2 vibrational level relative to the zero-point vibration level in both the (A) over tilde and (X) over tilde states. (C) 1997 Academic Press.