Effective diffusion times in multiple-pulse PFG diffusion measurements in porous media

Expressions for the effective diffusion times in multiple-gradient pulse diffusion measurements in liquid-saturated porous media are derived. This is necessary since the diffusion coefficient is time dependent. The results are needed for quantitative interpretation of the results of PFG diffusion measurements using the multiple-alternating-gradient schemes which are preferred for the majority of porous systems. The essence of the calculation and the results for ''square'' and ''sine'' pulse shapes have appeared previously, but without derivation. The details of this somewhat technical calculation may be needed by users. (C) 1996 Academic Press, Inc.