화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.101, No.23, 4149-4155, 1997
Photolysis of Na+(Cryptand(2.2.2))Na- - Photobleaching of Absorbency and Quenching of Fluorescence
The optical properties of the alkalide Na+(cryptand[2.2.2])Na+ are sensitive to the presence of defect electrons and can be dramatically altered by irradiation with light. Fluorescence intensities decrease markedly at excitation power densities above about 1 mW cm(-2), even though this power level is some 10(7) times lower than that required to affect the absorbance. Partial recovery occurs in powder samples over a period of several minutes at 30-100 K. The enhanced quenching of fluorescence is attributed to the presence of photoproduced trapped electrons. Pronounced changes occur in the optical absorbance spectra of vapor-deposited thin films of Na+(cryptand[2.2.2])Na- following irradiation by high intensity doubled- and tripled-YAG laser pulses. The effects are attributed to the intermediate formation of a "p-band metal" in which half of the electrons in the ground s(2) state of Na- are Promoted to the p-level, resulting in a high concentration of electrons trapped at some distance from the parent anion site.