Unidirectional Vibrational Energy Flow in Nitrobenzene
Unidirectional Vibrational Energy Flow in Nitrobenzene
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DOI：
10.1021/jp3127863
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发表时间：
2013-07-25
影响因子：
2.9
通讯作者：
Dlott, Dana D.
中科院分区：
文献类型：
--
作者：
Pein, Brandt C.;Sun, Yuxiao;Dlott, Dana D.
在环境温度下对硝基苯液体进行了实验，以探测硝基与苯基之间的振动能量流动。采用红外泵浦、拉曼探针法。利用量子化学计算将硝基苯的正常模式分为三大类：苯基模式、硝基模式和全局模式。在2500- 3500cm（-1）的红外波长范围内，产生的激发效果最好，最初定位在硝基或苯基上。2880 cm（-1）处的脉冲激发了一个硝基拉伸组合带。3080 cm（-1）的脉冲激发了苯基C-H拉伸和一些硝基拉伸。在硝基激发下，没有检测到向苯基的能量转移。苯基激发没有直接向硝基转移，但有向苯基-硝基拉伸等全局模态转移，因此苯基上的部分振动振幅向硝基转移。因此，从硝基到苯基的能量转移是不存在的，而从苯基到硝基的能量转移是微弱的。本文描述的实验方法可用于研究振动能量从分子的一部分到另一部分的流动，这有助于分子电子学和声子学的分子设计。当硝基与苯基基团连接时，硝基的振动隔离表明，强烈的非热反应途径可能在具有外围硝基的含能材料的冲击引发中起重要作用。
Experiments were performed on nitrobenzene liquid at ambient temperature to probe vibrational energy flow from the nitro group to the phenyl group and vice versa. The IR pump, Raman probe method was used. Quantum chemical calculations were used to sort the normal modes of nitrobenzene into three categories: phenyl modes, nitro modes, and global modes. IR wavelengths in the 2500-3500 cm(-1) range were found that best produced excitations initially localized on nitro or phenyl. Pulses at 2880 cm(-1) excited a nitro stretch combination band. Pulses at 3080 cm(-1) excited a phenyl C-H stretch plus some nitro stretch. With nitro excitation there was no detectable energy transfer to phenyl. With phenyl excitation there was no direct transfer to nitro, but there was some transfer to global modes such as phenyl-nitro stretching, so some of the vibrational amplitude on phenyl moved onto nitro. Thus energy transfer from nitro to phenyl was absent, but there was weak energy transfer from phenyl to nitro. The experimental methods described here can be used to study vibrational energy flow from one part of a molecule to another, which could assist in the design of molecules for molecular electronics and phononics. The vibrational isolation of the nitro group when attached to a phenyl moiety suggests that strongly nonthermal reaction pathways may play an important role in impact initiation of energetic materials having peripheral nitro groups.