Watching Hydrogen Bonds Break: A Transient Absorption Study of Water.
Watching Hydrogen Bonds Break: A Transient Absorption Study of Water.
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DOI：
10.1021/jp046711r
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发表时间：
2004-12
期刊：
影响因子：
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通讯作者：
T. Steinel;J. Asbury;Junrong Zheng;M. Fayer
中科院分区：
文献类型：
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作者：
T. Steinel;J. Asbury;Junrong Zheng;M. Fayer
超快红外瞬态吸收测量的完整的羟基OD拉伸模式光谱的HOD在水中，从100 fs到几十皮秒，观察氢键断裂和监测的氢键网络在水中的平衡。此外，振动寿命，氢键断裂的时间常数，和取向弛豫率被确定。氢键断裂过程的反应物和光产物光谱通过将瞬态光谱分解成两个分量来确定，即与振动激发态（反应物）相关联的初始光谱和与断裂的氢键（光产物）相关联的长时间光谱。通过适当地考虑到扰动的反应物光谱衰减的增长的光产物光谱，它被发现，振动弛豫（1.45 ps）和取向弛豫（1.53 ps）是波长无关的，因此，独立的氢键的程度。通过振动弛豫沉积到水中的能量不会通过预解离立即破坏氢键，也不会在升高的温度下产生热平衡的氢键分布。在通过振动弛豫沉积能量之后，氢键断裂时间为800 fs，并且存在几皮秒的瞬态期，在此期间氢键分布不处于热平衡。
Ultrafast infrared transient absorption measurements of the complete hydroxyl OD stretching mode spectrum of HOD in water, from 100 fs to tens of picoseconds, observe hydrogen bond breaking and monitor the equilibration of the hydrogen bond network in water. In addition, the vibrational lifetime, the time constant for hydrogen bond breaking, and the rate of orientational relaxation are determined. The reactant and photoproduct spectra of the hydrogen bond breaking process are identified by decomposing the transient spectra into two components, the initial spectrum associated with vibrational excited states (reactants) and the long-time spectrum associated with broken hydrogen bonds (photoproducts). By properly taking into account the perturbation of the reactant spectrum decay by the growth of the photoproduct spectrum, it is found that the vibrational relaxation (1.45 ps) and orientational relaxation (1.53 ps) are wavelength independent and, therefore, independent of the degree of hydrogen bonding. Energy deposited into water by vibrational relaxation does not immediately break a hydrogen bond by predissociation nor produce a thermally equilibrated hydrogen bond distribution at an elevated temperature. Following deposition of energy by vibrational relaxation, the hydrogen bond breaking time is 800 fs, and there is a transient period of several picoseconds during which the hydrogen bond distribution is not in thermal equilibrium.