Institute for Chemistry and Biochemistry/Crystallography, Freie Universität Berlin, Taku Str. 6, 14195 Berlin, Germany.
J Chem Phys. 2011 Jan 14;134(2):024518. doi: 10.1063/1.3518367.
We present a model for quasielastic neutron scattering (QENS) by an aqueous solution of compact and inflexible molecules. This model accounts for time-dependent spatial pair correlations between the atoms of the same as well as of distinct molecules and includes all coherent and incoherent neutron scattering contributions. The extension of the static theory of the excluded volume effect [A. K. Soper, J. Phys.: Condens. Matter 9, 2399 (1997)] to the time-dependent (dynamic) case allows us to obtain simplified model expressions for QENS spectra in the low Q region in the uniform fluid approximation. The resulting expressions describe the quasielastic small-angle neutron scattering (QESANS) spectra of D(2)O solutions of native and methylated cyclodextrins well, yielding in particular translational and rotational diffusion coefficients of these compounds in aqueous solution. Finally, we discuss the full potential of the QESANS analysis (that is, beyond the uniform fluid approximation), in particular, the information on solute-solvent interactions (e.g., hydration shell properties) that such an analysis can provide, in principle.
我们提出了一种用于描述水溶液中紧凑且不易变形分子的准弹性中子散射（QENS）的模型。该模型考虑了相同和不同分子原子之间的时变空间对关联，并包含了所有相干和非相干的中子散射贡献。静态排除体积效应理论的扩展[A. K. Soper, J. Phys.: Condens. Matter 9, 2399 (1997)]到时变（动态）情况，使得我们可以在均匀流体近似下获得低 Q 区 QENS 谱的简化模型表达式。所得的表达式很好地描述了天然和甲基化环糊精的 D(2)O 溶液的准弹性小角中子散射（QESANS）谱，特别是这些化合物在水溶液中的平移和旋转扩散系数。最后，我们讨论了 QESANS 分析的全部潜力（即超出均匀流体近似），特别是该分析可以提供的关于溶质-溶剂相互作用（例如，水合壳性质）的信息，原则上可以提供这些信息。
