Ab initio calculation of predissociation linewidths in the Schumann-Runge bands of the oxygen molecule

Ab initio multireference single- and double-excitation configuration interaction;calculations have been carried out for potential curves df the B (3)Sigma (-)(u), (1)Pi (u), (3)Pi (u), (5)Pi (u), and (3)Sigma (+)(u) electronic states of the O-2 molecule. Spin-orbit interaction matrix elements-among the above states and rotational interaction matrix elements between the B (3)Sigma (-)(u) and the (3)Pi (u) states have been evaluated in order to investigate the observed line broadening in the Schumann-Runge bands. Predissociation linewidths of rovibrational levels of the B (3)Sigma (-)(u) State are determined by using the complex rotation method in conjunction with the Gauss-Hermite quadrature procedure. It has been found that the (5)Pi (u) and (3)Pi (u) states play dominant roles in the predissociation of the B (3)Sigma (-)(u) state. The calculated linewidths for rovibrational levels of v = 0-13, N = 0 - 36 of the F-2 fine-structure components of the B (3)Sigma (-)(u) state are in very good agreement with experimental results. Isotopic effects in the predissociation of the B (3)Sigma (-)(u) State are studied by means of calculations for O-18(2) and (OO)-O-16-O-18 and the theoretical results are found to be in good agreement with the observed average predissociation linewidths in each case. (C) 2001 American Institute of Physics.