MEASUREMENT OF THE QUANTUM YIELD OF TRIPLET FORMATION (PHI-ISC) IN A POLYMER MATRIX BY THE TIME-RESOLVED THERMAL LENS METHOD - EXCITATION WAVELENGTH DEPENDENCE OF PHI-ISC OF N-METHYL-PARA-NITROANILINE

The time-resolved thermal lens method is demonstrated to be suitable for measuring the quantum yield of the triplet formation (φISC) of organic molecules in a polymer matrix at room temperature when triplet lifetimes at low temperature are longer than the thermal diffusion time. This method is applied to the measurement of φISC of N-methyl-p-nitroaniline in poly(methyl methacrylate) as a function of the excitation wavelength. The excitation wavelength dependence of the intensity ratio of phosphorescence to fluorescence is discussed on the basis of this result. © 1990.