Vibrational Energy Relaxation of Water Molecules in a Hydrated Lithium Nitrate Crystal
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- 作者：Wilbert J. Smit ; Huib J. Bakker
- 刊名：Journal of Physical Chemistry C
- 出版年：2016
- 出版时间：May 26, 2016
- 年：2016
- 卷：120
- 期：20
- 页码：11078-11084
- 全文大小：413K
- 年卷期：0
- ISSN：1932-7455
文摘
Water molecules in hydrated salts often have a well-defined geometrical arrangement and form an excellent model system for studying the effects of the hydrogen-bond environment on vibrational energy relaxation. Hydrated lithium nitrate contains two distinct types of crystal water molecules. One water molecule makes strong and weak hydrogen bonds; the other water molecule makes two bifurcated hydrogen bonds. We use femtosecond two-dimensional infrared spectroscopy to probe the vibrational relaxation dynamics of the OD stretch vibration of dilute HDO molecules in lithium nitrate trihydrate. In the temperature range from 22 to 295 K we observe a decrease in vibrational lifetime from 3.8 ± 0.2 to 2.8 ± 0.1 ps for the strongly hydrogen-bonded species, from 5.41 ± 0.08 to 4.14 ± 0.05 ps for the bifurcated hydrogen-bonded species, and from 10.4 ± 0.2 to 8.8 ± 0.4 ps for weakly hydrogen-bonded species. This temperature dependence is opposite to that of the OD stretch vibration of dilute HDO:H2O ice, for which the vibrational lifetime increases from 480 ± 40 fs at 25 K to 850 ± 60 fs at 265 K. We discuss the origin of this difference in temperature dependence.