Isotope Effects on Deuterium Spin-Lattice Relaxation in H2O/D2O Mixtures

Masato Kakihana, Makoto Okamoto, Tadashi Nagumo

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    1 Citation (Scopus)

    Abstract

    The deuterium spin-lattice relaxation time, T1, of H2O/D2O mixtures is measured at 298.2 K. The relaxation rate, [FORMULA OMITTED], is found to increase with increasing deuterium atom fraction, n, the plot of [FORMULA OMITTED] vs. n exhibiting a small depature from linearity. A general equation [FORMULA OMITTED] (n) for the H2O/ D2O system is formulated. The temperature dependence of T1 is investigated in the temperature range 278.2 K to 298.2 K for n = 6.8 × 10−3, 6.8 × 10−2, 0.244, 0.500, and 0.997. On the assumption that the electric field gradient parameters (e2 q Q/h and δ) are independent of n and temperature, an effective correlation time, τc, eff, is derived from the T1 data. Relatively large isotope effects on τc, eff are found; possible reasons for the existence of such isotope effects are discussed in terms of a simple Debye model. The mean activation enthalpy ([FORMULA OMITTED] H) and entropy ([FORMULA OMITTED] S) for the relaxation process within the temperature range studied are derived on the basis of Eyring’s absolute rate theory and the temperature dependence of τc, eff. Both activation parameters are found to increase linearly with n: [FORMULA OMITTED] H/kJ mol−1 = 18.2 + 2.46 n, [FORMULA OMITTED] S/J K−1 mol−1 = 37.5 + 6.77 n.

    Original languageEnglish
    Pages (from-to)1085-1095
    Number of pages11
    JournalZeitschrift fur Naturforschung - Section A Journal of Physical Sciences
    Volume40
    Issue number11
    DOIs
    Publication statusPublished - 1985 Nov 1

    ASJC Scopus subject areas

    • Mathematical Physics
    • Physics and Astronomy(all)
    • Physical and Theoretical Chemistry

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