Vacuum ultraviolet fluorescence excitation spectrum of I2

Abstract

A detailed study of the vacuum ultraviolet fluorescence excitation spectrum of I2 in the region 110–210 nm is reported. Both absorption and fluorescence excitation spectra were recorded simultaneously using continuously tunable synchrotron radiation. At long wavelengths (176–210 nm) the fluorescence excitation spectrum is dominated by the D(0+u) ion-pair state. Perturbations between the D(0+u) state and isoenergetic levels of the c6 Rydberg state lead to pronounced resonances (dips) in the fluorescence excitation spectrum. Weaker absorption to the F(0+u) and F′(0+u) ion-pair states is identified at 170 and 150 nm, respectively. Below 149 nm electronically excited iodine atoms (I 6s 4P5/2 and I 6s 2P3/2) are formed by predissociation of high-lying Rydberg and ion-pair states.