A HIGH-RESOLUTION O-18 ISOTOPE STUDY IN THE VACUUM-ULTRAVIOLET OF THEA(1)PI-]X(1)SIGMA(+) 4TH POSITIVE SYSTEM OF CO

High-resolution jet emission spectra of (CO)-C-12-O-18 in the 1380-165 0 Angstrom region of the 4th positive bands, A (1) Pi --> X (1) Sigma( +), have been recorded photographically and have been reduced to upper -state term values for low to medium rotational quantum numbers in the 10 lowest vibrational levels of A (1) Pi. The deperturbation of the A state from spin-orbit and rotation-electronic interactions with singl et and triplet Sigma and Delta states has established the percentage ( 1) Pi character of the observed excited-state rovibronic levels. Dunha m series expansion coefficients representing the deperturbed energies have also been determined.