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

Masato Kakihana, Makoto Okamoto, Tadashi Nagumo

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1 Citation (Scopus)


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
Issue number11
Publication statusPublished - 1985 Nov 1
Externally publishedYes

ASJC Scopus subject areas

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


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