ABSTRACT
From a comparison with the spectrum of NiF, a low-lying (2)Sigma(+) state is expected to lie in the first 2000 cm(-1) above the ground X(2)Pi(3/2) state of NiCl. The identification of this (2)Sigma(+) (v = 0) state (at 1768 cm(-1)) has been carried out through the analysis of two electronic transitions (2)Pi(3/2)-(2)Sigma(+) (22 720 cm(-1)) and (2)Pi(1/2)-(2)Sigma(+) (23 210 cm(-1)) recorded by high-resolution Fourier transform spectroscopy. Dispersed fluorescence spectroscopy allowed these transitions to be located on an absolute energy-level diagram that includes the previously studied electronic states. Copyright 2000 Academic Press.
ABSTRACT
The A'(1)Pi-X(1)Sigma(+) near-infrared system of CaO was observed for the first time at high resolution using a Fourier transform spectrometer. The A'(1)Pi-X(1)Sigma(+) chemiluminescence was excited in a Ca + N(2)O flame produced in a Broida-type oven. More than 3000 rotational lines, classified into 19 bands involving the A'(1)Pi 0 = v' = 3 and the X(1)Sigma(+) 1 = v" = 7 vibrational levels were measured in the 4000-10 000 cm(-1) region with a precision of 0.005 cm(-1). The X(1)Sigma(+) (v = 0, 1) millimeter-wave and X(1)Sigma(+) (v = 0-3) infrared data available in the literature were merged with our new electronic data in order to obtain improved Dunham constants for the ground state of CaO. Very peculiar perturbations are observed in the higher vibrational levels of the A'(1)Pi state, so the upper levels of transitions with v' = 2 and 3 were represented by term values in our least-squares analysis. The interaction of the A'(1)Pi (v >/= 2) levels with the nearby b(3)Sigma(+) (v-2) levels has been detected. An extended set of A'(1)Pi (v = 0-3) data has been obtained which is suitable for use in a future multistate deperturbation analysis of the a(3)Pi approximately A'(1)Pi approximately b(3)Sigma(+) approximately A(1)Sigma(+) complex of excited states. The new near-infrared spectra of the A'(1)Pi-X(1)Sigma(+) transition of CaO also permits the first direct high-resolution linkage between the orange and green systems and the near-infrared bands. Copyright 2000 Academic Press.