Photoabsorption properties of cellulose fibres under continuous and modulated irradiation were investigated in situ by the use of reversed double-beam photoacoustic spectroscopy (RDB-PAS). This photoacoustic (PA) measurement enabled observation of ultraviolet- and visible light-induced, electron trap filling, and reductive change on the surface of the fibres. Energy-resolved measurements and analysis of the kinetics of photoinduced de-excitation suggested that electrons that accumulated in the different cellulose crystalline phases had moderate reactivity toward molecular oxygen. Saturation limits of the intensities of the PA and RDB-PAS signals under de-aerated conditions in the presence of surface-adsorbed methanol were estimated for softwood and hardwood cellulose samples. The results suggest that the RDB-PAS technique is a feasible method for the estimation of the electron trap distribution, which is a potential measure of the density of crystalline cellulose defects.

通过使用反向双光束光声光谱 (RDB-PAS) 原位研究了纤维素纤维在连续和调制辐照下的光吸收特性。这种光声 (PA) 测量能够观察到紫外光和可见光引起的、电子陷阱填充以及纤维表面的还原变化。能量分辨测量和光致去激发动力学分析表明，在不同纤维素结晶相中积累的电子对分子氧具有中等反应性。对于软木和硬木纤维素样品，在脱气条件下，在存在表面吸附甲醇的情况下，估计了 PA 和 RDB-PAS 信号强度的饱和极限。