The synchrotron radiation (SR) induced, vacuum ultraviolet (vacuum UV) photodegradation of polystyrene was studied by fluorescence spectroscopy. Two broad, structureless transitions were observed in the dispersed fluorescence spectrum of polystyrene when wavelengths shorter than 2200 Á were used to excite the polymer films: the first was centered at 3200 Á, and the second was centered at 5300 Á. The fluorescence excitation spectrum of each emission band has been recorded from 450 to 3000 Á and is compared to the optical absorption spectrum of polystyrene from 1050 to 3000 Á. The 3200-Á band is due to an excimer to ground state transition. The 5300-Á band is due to fluorescence from a conjugated backbone structure which forms when the polystyrene films are exposed to vacuum UV radiation. Changes were observed in both the fluorescence and fluorescence excitation spectra following exposure to 1200-Á or broad-band SR. Based on the data, a qualitative model is used to account for the degradation and energy transfer within the polystyrene films.

The high-resolution Al L-edge x-ray-absorption near-edge structure from single-crystal sapphire has been recorded by measuring the total-electron yield and x-ray-fluorescence yield with synchrotron radiation. The edge structures up to 11 eV from the absorption edge are assigned in terms of the transitions of Al 2p electrons to empty levels using molecular-orbital calculations. The post-edge features between 11 and 60 eV above the Al L» absorption edge were found to correlate very well with the interatomic distances from the absorbing atom to its neighboring atoms as predicted by the multiple-scattering model.

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Supercritical fluid techniques continue to grow in importance in analytical chemistry, especially supercritical fluid chromatography (1). Accompanying this growth is the development of postcolumn detection methods, including flame ionization detection (2,3), inductively coupled plasma emission (4), mass spectrometry (5, 6), and supersonic jet spectroscopy (7-9). In each of these detection methods, the behavior of