Study on the molecular structure of the photo induced phase in TTF-CA crystal by time-resolved Fourier transform infrared spectroscopy

研究了528 nm脉冲激光辐照四硫富瓦烯对氯苯醚(TTF-CA)体晶和薄晶在亚微秒时间范围内傅里叶变换红外光谱的变化。在TTF-CA大块晶体的时间分辨反射光谱中，我发现由于CA分子的羰基伸缩振动引起的激发反射峰出现在与热平衡的离子相和中性相不同的位置。该瞬时反射峰为CA分子在光诱导相中的羰基伸缩振动。通过与具有不同离子状态的CA分子的暂态峰位置的比较，确定光诱导相的电荷转移程度为0.5。用TTF-CA薄晶进行的时间分辨红外吸收光谱的测量证实了这一结果。

I have studied the change of Fourier transform infrared spectrum of tetrathiafulvalene-p-chloranil (TTF-CA) bulk and thin crystals induced by 528-nm pulsed laser irradiation in the sub-micro-seconds time range. In the time-resolved reflection spectroscopy with TTF-CA bulk crystal, I found that the excitation-induced reflection peak ascribed to the carbonyl-stretching vibration of CA molecules appears at the different position from ionic and neutral phases in thermal equilibrium. The transient reflection peak was concluded to the carbonyl stretching vibration of CA molecules in the photo-induced phase. The degree of charge transfer of the photo-induced phase was evaluated to be 0.5 by the comparison of the position of the transient peak with those of the CA molecules with distinct ionic states. These results were reconfirmed by the measurement of the time-resolved infrared absorption spectroscopy with TTF-CA thin crystals.