Low-Temperature Vibrational Energy Transport via PEG Chains
Low-Temperature Vibrational Energy Transport via PEG Chains
复制标题
通过 PEG 链进行低温振动能量传输
DOI：
10.1021/acs.jpclett.0c01273
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Rubtsov, Igor V.
中科院分区：
文献类型：
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作者：
Mackin, Robert T.;Leong, Tammy X.;Rubtsova, Natalia I.;Burin, Alexander L.;Rubtsov, Igor V.
我们使用弛豫辅助的二维红外光谱研究温度依赖性（10-295 K）的端到端的能量传输通过末端修饰的PEG低聚物的各种链长。通过激发2100 cm-1处的叠氮基端基伸缩模式引入过量能量（tag）;通过观察1740 cm-1处琥珀酰亚胺酯端基的不对称C = O伸缩模式记录传输。整体运输涉及末端基团处的扩散步骤和通过PEG链的弹道步骤。我们发现，在较低的温度下，通过链的能量传输变得更快，而端基扩散传输时间和标签寿命增加。使用量子刘维尔方程的运输模型连接的观察到的退相干率的减少和振动波包的平均自由程的增加。在低温下，由于非谐能量再分配途径的数量和效率的降低，端基处的能量传输减慢。
We used relaxation-assisted two-dimensional infrared spectroscopy to study the temperature dependence (10–295 K) of end-to-end energy transport across end-decorated PEG oligomers of various chain lengths. The excess energy was introduced by exciting the azido end-group stretching mode at 2100 cm–1(tag); the transport was recorded by observing the asymmetric C═O stretching mode of the succinimide ester end group at 1740 cm–1. The overall transport involves diffusive steps at the end groups and a ballistic step through the PEG chain. We found that at lower temperatures the through-chain energy transport became faster, while the end-group diffusive transport time and the tag lifetime increase. The modeling of the transport using a quantum Liouville equation linked the observations to the reduction of decoherence rate and an increase of the mean-free-path for the vibrational wavepacket. The energy transport at the end groups slowed down at low temperatures due to the decreased number and efficiency of the anharmonic energy redistribution pathways.