Different time-scale relaxation dynamics in organic supramolecular ferroelectrics studied by linear and nonlinear spectroscopy
Different time-scale relaxation dynamics in organic supramolecular ferroelectrics studied by linear and nonlinear spectroscopy
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通过线性和非线性光谱研究有机超分子铁电体中不同时间尺度的弛豫动力学
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发表时间：
2015
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影响因子：
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通讯作者：
Y. Okimoto
中科院分区：
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作者：
T. Umanodan;Sei’ichi Tanaka;S. Naruse;T. Ishikawa;K. Onda;S. Koshihara;S. Horiuchi;Y. Okimoto
研究了质子化2，3-二（2-吡啶基）吡嗪（H-dppz）和去质子化氯冉酸（Hca）组成的有机超分子铁电材料的时间分辨线性和非线性光学响应。我们将纳秒激光脉冲（λ = 532 nm）照射到晶体上，泵浦Hca分子的分子内激发，并在光激发后观察到C=O和C-O−分子振动模式的明显红移。每个软化模式在不同的时间尺度上逐渐松弛，表明Hca分子的电子在光激发后重新分布。通过相同的激发，观察到二次谐波（SH）强度的大的抑制，由转移质子的宏观无序驱动。SH强度的衰减时间比振动模的衰减时间长，表明微观振动和宏观铁电性在不同的时间尺度上具有动力学性质。
Time-resolved linear and nonlinear optical responses were investigated in an organic supramolecular ferroelectric material composed of protonated 2,3-di(2-pyridinyl)pyrazine (H-dppz) and deprotonated chloranilic acid (Hca). We irradiated nanosecond laser pulses (λ = 532 nm) on the crystal, pumped the intramolecular excitation of the Hca molecule, and observed a clear redshift of the molecular vibrational modes of C=O and C–O− just after the photoexcitation. Each softened mode gradually relaxed on different time scales, indicating that the electrons of the Hca molecules were redistributed after the photoexcitation. By the same excitation, a large suppression of the second-harmonic (SH) intensity was observed, driven by the macroscopic disordering of the transferred protons. The decay time of the SH intensity was longer than those of the vibrational modes, suggesting that the microscopic vibrations and macroscopic ferroelectricity have dynamics on different time scales.