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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Vibrational Energy Dynamics of Normal and Deuterated Liquid Benzene
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Vibrational Energy Dynamics of Normal and Deuterated Liquid Benzene

机译：普通和氘代液态苯的振动能动力学

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摘要

Ultrafast Raman spectroscopy with infrared (IR) excitation is used to study vibrational energy dynamics of ambient temperature liquids benzene and benzene-d(6). After IR pumping of a CH-stretch or CD-stretch parent excitation, the redistribution of vibrational energy is probed with anti-Stokes Raman. Ten benzene or 12 benzene-d(6) vibrations out of 30 total have large enough cross sections to be observed. The pathways, quantum yields, and lifetimes for energy transfer among these vibrations are quantified. Using a CCl4 molecular thermometer, we demonstrate an ultrafast Raman calorimetry method which allows measurement of the rate that benzene vibrational energy is dissipated into the bath. On the basis of energy conservation, we then determine the time-dependent dissipation of aggregate vibrational energy from the unobserved, "invisible" vibrations. During the similar to 1 ps IR excitation process. vibrational energy is coherently redistributed to several vibrational modes ("coherently" means the rate is faster than (T-2)(-1) of the pumped transition). This energy is then further redistributed in an incoherent intramolecular vibrational relaxation process with a 6 ps T, time constant. The subsequent dynamics involve energy transfer processes accompanied by vibrational energy dissipation to the bath. This vibrational cooling process has a half-life of 30 ps in benzene and 20 ps in benzene-d(6), and thermalization is complete in similar to 100 ps. The observed strongly Raman-active vibrations have about the same amount of energy per mode as the invisible vibrations. The invisible vibrational energy in benzene decays somewhat faster than the observed energy. These two decay rates are about the same in benzene-d(6).
机译：具有红外（IR）激发的超快速拉曼光谱用于研究环境温度下液体苯和苯-d（6）的振动能动力学。红外泵送CH拉伸或CD拉伸母体激发后，用反斯托克斯拉曼光谱仪探测振动能量的重新分布。 30次振动中有10次苯或12次苯-d（6）振动具有足够大的横截面，可以观察到。量化了这些振动之间的能量传递途径，量子产率和寿命。使用CCl4分子温度计，我们演示了超快拉曼量热法，该方法可以测量苯振动能消散到浴中的速率。然后，在能量守恒的基础上，我们从未观察到的“不可见”振动中确定了总振动能量随时间的消散。在类似于1 ps的IR激发过程中。振动能量被连贯地重新分配给几个振动模式（“相干”表示速率比泵浦过渡的（T-2）（-1）快）。然后，该能量将以不连续的分子内振动弛豫过程进一步重新分配，时间常数为6 psT。随后的动力学涉及能量传递过程，伴随振动能量消散到浴槽中。这种振动冷却过程在苯中的半衰期为30 ps，在苯-d（6）中的半衰期为20 ps，并且完全以约100 ps的速率完成热化。观察到的强拉曼主动振动每个模式的能量与不可见振动大约相同。苯中的无形振动能量的衰减比观察到的能量要快一些。在苯-d（6）中，这两个衰减率大致相同。

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