5π_{u 3/2}→6sR Bands

Fluorescence Dips

The excited XeF₂^* molecule in the Rydberg states are preferentially dissociated to the product channels leading to non-radiative fragments. A most interesting and distinct observation is made for the series of 5π_{u 3/2}→6sR bands around 143 nm concerning the efficient quenching of the excited state. Note that no peaks are observed in the fluorescence excitation spectrum in spite of intense absorption bands (30 − 40 Mb) observed.

These findings would be explained by the obvious reason that this Rydberg state is quite efficiently channelled into non-radiative dissociation products, Xe + 2F. If one carefully examines the fluorescence excitation spectrum, even dips are found at 143.18 and 144.25 nm, whereas weak positive bands are observed at 141.04 and 142.11 nm. It seems that the fluorescence bands which are negative at lower energies tend to become positive as the exciting light energy is increased.