EXTREME ULTRAVIOLET PHOTODISSOCIATION OF O2 VIA THE FREE (C4-SIGMA-U-)3S-SIGMA-G STATE AS PROBED BY DISPERSED VACUUM ULTRAVIOLET FLUORESCENCE

Dispersed vacuum ultraviolet (VUV) fluorescence spectra of neutral fragments formed in the extreme ultraviolet photodissociation of O2 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 O2 in superexcited states. The VUV fluorescence from dissociation fragments has been observed at the lowest dissociation limits of O(n(l)) + O(3P). The dissociation of the Rydberg states converging on the O2+(b4-SIGMA(g)-) and O2+(B2-SIGMA(g)-) states has been shown to prefer dissociation limits higher than the lowest limit of O(3s3S)+O(3P) via multichannel crossing. An intensity enhancement in the O(3s3S-->3P) fluorescence excitation spectrum (FES) around the incident wavelength of 58 nm has been explained by the direct dissociation of the free (c4-SIGMA(u)-)3s-sigma(g) state.