Indirect predissociation of the 3p pi(u) f(1)Sigma(+)(u) state of O-2

Absolute photoabsorption cross sections for bands of the 3p pi(u) f(1) Sigma(u)(+) <-- X(3) Sigma(g)(-) transition of O-16(2) have been measured. The measurements were taken using narrow-bandwidth vacuum ultraviolet radiation generated by third-order frequency mixing in Xe and Kr of excimer-pumped dye laser radiation. The oscillator strengths and predissociation linewidths of the observed bands are found to vary irregularly with vibration, and some bands exhibit predissociation linewidths which increase rapidly with rotation. Theoretical modelling of the spectra using the coupled-channel Schrodinger equations technique shows that the principal channel for predissociation of the f state is the (3) Sigma(u)(-) valence-state continuum, through an intermediate interaction between the f state and the neighbouring 3p pi(u) 3 Sigma(u)(-) Rydberg state. We also show that there is a significant interference contribution to the strengths of these bands from the f(1) Sigma(u)(+) <-- b(1) Sigma(g)(+) transition.