INDIRECT PREDISSOCIATION OF THE 3P-PI(U) F(1)SIGMA(-2()(U) STATE OF O)

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 meas ured. The measurements were taken using narrow-bandwidth vacuum ultrav iolet radiation generated by third-order frequency mixing in Xe and Kr of excimer-pumped dye laser radiation. The oscillator strengths and p redissociation linewidths of the observed bands are found to vary irre gularly with vibration, and some bands exhibit predissociation linewid ths which increase rapidly with rotation. Theoretical modelling of the spectra using the coupled-channel Schrodinger equations technique sho ws that the principal channel for predissociation of the f state is th e (3) Sigma(u)(-) valence-state continuum, through an intermediate int eraction between the f state and the neighbouring 3p pi(u) 3 Sigma(u)( -) Rydberg state. We also show that there is a significant interferenc e contribution to the strengths of these bands from the f(1) Sigma(u)( +) <-- b(1) Sigma(g)(+) transition.