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| - Photolysis of Na+(Cryptand[2.2.2])Na-: Photobleaching of Absorbance and Quenching ofFluorescence
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| - The optical properties of the alkalideNa+(cryptand[2.2.2])Na-are sensitive to the presence of defect electronsand can be dramatically altered by irradiation with light.Fluorescence intensities decrease markedly atexcitation power densities above about 1 mWcm-2, even though this power level is some107 times lowerthan that required to affect the absorbance. Partial recoveryoccurs in powder samples over a period ofseveral minutes at 30−100 K. The enhanced quenching offluorescence is attributed to the presence ofphotoproduced trapped electrons. Pronounced changes occur in theoptical absorbance spectra of vapor-deposited thin films ofNa+(cryptand[2.2.2])Na-following irradiation by high intensity doubled- andtripled-YAG laser pulses. The effects are attributed to the intermediateformation of a “p-band metal” in which halfof the electrons in the ground s2 state ofNa- are promoted to the p-level, resulting in a highconcentrationof electrons trapped at some distance from the parent anionsite.
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