Extreme ultraviolet photodissociation of O2 via the free (c 4Σ−u)3sσg state as probed by dispersed vacuum ultraviolet fluorescence

Abstract Dispersed vacuum ultraviolet (VUV) fluorescence spectra of neutral fragments formed in the extreme ultraviolet photodissociation of O 2 and their excitation spectra at the incident synchrotron radiation (SR) wavelength of 57–85 nm have been obtained using a secondary VUV monochromator to clarify the dissociation mechanism of O 2 in superexcited states. The VUV fluorescence from dissociation fragments has been observed at the lowest dissociation limits of O( n l)+O( 3 P). The dissociation of the Rydberg states converging on the O + 2 (b 4 Σ − g ) and O + 2 (B 2 Σ − g ) states has been shown to prefer dissociation limits higher than the lowest limit of O(3s 3 S)+O( 3 P) via multichannel crossing. An intensity enhancement in the O(3s 3 S→ 3 P) fluorescence excitation spectrum (FES) around the incident wavelength of 58 nm has been explained by the direct dissociation of the free (c 4 Σ − u )3sσ g state.