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제114회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Dynamics of Water in Aqueous NaPF6 Solution At Different Temperatures

2014년 9월 1일 19시 30분 09초
PHYS.P-478 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
10월 15일 (수요일) 16:00~19:00
저자 및
남다영, 이치호, 박성남*
고려대학교 화학과, Korea
Direct measurements of the dynamics of water in ionic hydration shells apart from those of bulk water have been experimentally quite challenging because of the poor spectral distinction among water molecules in bulk and ionic hydration shells. Here, the dynamics of water in aqueous NaPF6 solution were studied at different temperatures by FTIR and IR pump-probe spectroscopy. The OD stretch band in the FTIR spectra of aqueous NaPF6 solution was able to be separated into the contributions from three distinct subsets of water: (1) water molecules in bulk (ODW), (2) water molecules in the hydration shells of Na+ ions(ODC), and water molecules hydrogen-bonded to PF6- ions (ODA). Temperature-dependent FTIR experimental results indicate that the water structure around ions is more rigid and less changed than in bulk water with increasing temperature. Polarization-controlled IR pump-probe experiments were used to study vibrational population relaxation, P(t), and orientational anisotropy decay, r(t), of water in different subsets. The vibrational lifetimes of ODW, ODC, and ODA in aqueous 5.0 M NaPF6 solution were directly determined and found to be independent of temperature up to 50 ℃. In contrast, orientational relaxation dynamics of water became faster when the temperature was increased in aqueous NaPF6 solution and the activation energies for water orientation were determined from the temperature-dependent orientational relaxation time. In our present experiments, the individual dynamics of water in bulk and ionic hydration shells in aqueous NaPF6 solutions were able to be studied in more detail.