Hydration Dynamics of Aqueous Nitrate
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- 作者：Jan Th酶gersen ; Julien R茅hault ; Michael Odelius ; Tom Ogden ; Naresh K. Jena ; Svend J. Knak Jensen ; S酶ren R. Keiding ; Jan Helbing
- 刊名：The Journal of Physical Chemistry B
- 出版年：2013
- 出版时间：March 28, 2013
- 年：2013
- 卷：117
- 期：12
- 页码：3376-3388
- 全文大小：618K
- 年卷期：v.117,no.12(March 28, 2013)
- ISSN：1520-5207
文摘
Aqueous nitrate, NO3鈥?/sup>(aq), was studied by 2D-IR, UV鈥揑R, and UV鈥揢V time-resolved spectroscopies in combination with molecular dynamics (MD) simulations with the purpose of determining the hydration dynamics around the anion. In water, the D3h symmetry of NO3鈥?/sup> is broken, and the degeneracy of the asymmetric-stretch modes is lifted. This provides a very sensitive probe of the ion鈥搘ater interactions. The 2D-IR measurements reveal excitation exchange between the two nondegenerate asymmetric-stretch vibrations on a 300-fs time scale concomitant with fast anisotropy decay of the diagonal-peak signals. The MD simulations show that this is caused by jumps of the transition dipole orientations related to fluctuations of the hydrogen bonds connecting the nitrate ion to the nearest water molecules. Reorientation of the ion, which is associated with the hydrogen-bond breaking, was monitored by time-resolved UV鈥揑R and UV鈥揢V spectroscopy, revealing a 2-ps time constant. These time scales are very similar to those reported for isotope-labeled water, suggesting that NO3鈥?/sup>(aq) has a labile hydration shell.