De-excitation dynamics of Rydberg states in O2: I. Total cross sections for O I fluorescence emission following predissociation of 2σ- 1u(c4Σ- u)nσg3Σ-u states
Absolute cross sections for the total fluorescence emission between 97 and 131 nm by atomic oxygen formed after the photoexcitation of 2σ-1u(c4Σ- u)nσg3Σ- u Rydberg states in O2 and their successive predissociation were measured for the first time. The dissociation lifetimes and fluorescence yields were estimated using a stepwise model and the potential curve of the O2+2σ- 1u(c4Σ-u) state known from Beebe et al (Beebe N H F, Thulstrup E W and Andersen A 1976 J. Chem. Phys. 64 2080). The calculated lifetimes of the vibrational levels v = 0 and 1 of the 2σ-1u(c4Σ- u) state are 3.4×10-12 and 6.3×10-14 s, respectively. They agree with the measured data of Evans et al (Evans M, Stimson S, Ng C Y and Hsu C-W 1998 J. Chem. Phys. 109 1285) and are consistent with the results of the present experiment. The calculated lifetimes support the model of `fast' dissociation of the O2+2σ- 1u(c4Σ-u), v states in contrast to the earlier model of `slow' dissociation of Tanaka and Yoshimine (Tanaka K and Yoshimine M 1979 J. Chem. Phys. 70 1626).