Luminescence Quenching and Decay Processes in Multicomponent Systems: n-Nonane+p-Xylene+CCl4

Abstract

A monophoton technique to measure fast luminescence decay and utilizing pulsed uv excitation has been employed to determine specific rates of excitation quenching in systems containing n‐nonane+p‐xylene+CCl₄, with n‐nonane serving as an optically inert solvent, p‐xylene as scintillator, and CCl₄ as quencher. The decay‐time data are employed to evaluate the characteristic rate parameters k_q for quenching of p‐xylene luminescence by CCl₄. Values so obtained are in good agreement with values obtained from steady‐state studies. The variation in k_q with p‐xylene concentration is consistent with the view that energy migration as such via p‐xylene molecules occurs in addition to material diffusion of excited molecules. Dynamic and steady‐state measurements of self‐quenching in p‐xylene+n‐nonane systems indicate that, if excimer formation in p‐xylene occurs, it is followed by a very rapid nonradiative deactivation of the excimer. Furthermore, differences in the self‐quenching behavior as determined with steady‐state and decay‐time techniques suggest some form of static quenching in p‐xylene. This static quenching can be explained on the basis of clustering in the ground state.