Photophysical and photochemical processes of several aramatic molecules

用时间分辨和稳态测量方法研究了几种芳烃分子在超临界流体中的光物理和光化学过程，芘在CO_2超临界流体中的发射强度衰减曲线显示出12 ns的上升和100 ns的衰减。前者是激基缔合物的寿命，后者是受激芘的寿命。单体荧光强度与芘浓度成正比，激基缔合物荧光强度与芘浓度无关，并四苯在CO_2超临界流体中的吸收光谱在525 nm附近出现一个新的吸收带，归属于基态二聚体的吸收带。在550 nm处测量的发射强度衰减根据双指数函数、12 ns和22 ns进行分析。Cl-萘在CO_2超临界流体中的发射光谱由430-600 nm的微弱磷光发射和300-400 nm的普通单体荧光组成。荧光量子产率约为0.5，而磷光的量子产率约为10 μ g<-5>。在350 nm处测得的发射强度衰减为5 ns，而在500 nm处测得的发射强度衰减约为100 ns。

Photophysical and photochemical processes of several aromatic molecules were studied in supercritical fluids by means of time-resolved and steady- state measurements.The emission intensity decay curve of pyrene in the CO_2 supercritical fluid showed a 12 ns rise and a 100 ns decay. The former is that of the excimer lifetime, while the later is the lifetime of excited pyrene. The monomer fluorescence intensity was proportional to the concentrations of pyrene while that of excimer emission was nearly constant regardless of the concentrations.Absorption spectra of tetracene in the CO_2 supercritical fluid showed a new absorption band at around 525 nm which was assigned to that of the ground state dimer. The emission intensity decay measured at 550 nm were analyzed in terms of biexponential function, 12 ns and 22 ns. The lifetime of 12-13 ns is those of monomer and 22 ns is the dimer lifetime.The emission spectra of Cl-naphthalene in the CO_2 supercritical fluid consisted of the weak phosphorescence emission at around 430-600 nm as well as the ordinary monomer fluorescence appearing at around 300-400 nm. The fluorescence quantum yield was about 0.5 while that of the phosphorescence was about 10^<-5>. The emission intensity decay measured at 350 nm was 5 ns, while that measured at 500 nm was about 100 ns.