La luminescence différée du styrène en solution vitreuse dans le méthylcyclohexane

Abstract

The trapping of electrons and styrene cations and anions has been studied in a methylcyclohexane glass by the techniques of deferred luminescence. Radiothermoluminescence curves consist of two peaks, at 90 and 95°K, in this matrix. The second peak increases linearly with styrene concentration up to 2 × 10−2M when it reaches a constant value, whereas the first peak increases from 10−4 to 10−3M and then decreases at higher concentrations and is not discernible at concentrations above 10−2M. We propose two mechanisms which are qualitatively consistent with this behavior and are based essentially on the recombination of styrene cations with thermally detrapped electrons in the first peak and with anions in the second peak. Photothermoluminescence (i.e., thermoluminescence after photoionization with ultraviolet light) similarly consists of the 90 and 95°K peaks for a 10−3M solution and of the 95° peak alone for a 10−d M solution. Radiophotoluminescence excitation spectra at 77°K, corresponding to absorption spectra of trapped electrons and styrene anions, show that anions are the predominant negative species in 10−2 molar solution, and trapped electrons in 10−3 molar solution. Spectral analysis of radiothermoluminescenece shows the presence of two emission bands, one of which is identical with styrene fluorescence excited by the 254 Nm mercury line (λmax = 292, 302, 307, and 317 Nm). The other band has three fairly poorly resolved maxima at 474, 486 and 496 nm and seems to correspond to the fluorescence of C6H5ĊH‐CH3 radicals formed during radiolysis.