Spin echoes of nuclear magnetization diffusing in a constant magnetic field gradient and in a restricted geometry

摘要: We study the influence of restriction on Carr–Purcell–Meiboom–Gill spin echoes response magnetization spins diffusing in a bounded region presence constant magnetic field gradient. Depending three main length scales: LS pore size, LG dephasing and LD diffusion during half-echo time, regimes decay have been identified: free, localization motionally averaging regime. In regime, exponent depends fractional power (2/3) gradient, denoting strong breakdown second cumulant or Gaussian phase approximation (GPA). other two regimes, gradient squared, GPA holds. find that transition from to regime happens when gradients approach special values, corresponding branch points eigenvalues. Transition one another as function echo number for certain range parameters is discussed. ...