A Stimulated-Echo Method for Diffusion Measurements in Heterogeneous Media Using Pulsed Field Gradients

✍ Scribed by Geir Humborstad Sørland; Bjørn Hafskjold; Oddvin Herstad

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 237 KB
• Volume: 124
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1996.1029

✦ Synopsis

The pulsed-field-gradient stimulated-echo method is a wellbecomes small compared to the square of the applied gradiestablished technique for studying molecular motion without ent (1). The other approach is to use bipolar gradients todisturbing the system under investigation. In porous media, the gether with RF pulses in such a manner that the cross terms effects from internal magnetic field gradients make it necessary are canceled or reduced (2).

to perform compensatory sequences. Short relaxation times

Introducing several RF pulses into the sequence induces make it necessary to use as short pulse a sequence as possible. unwanted echoes which interfere with the uptake of the stim-Here a pulse sequence which gives reliable diffusion measureulated echo of interest. There exist numerous inventive sements without the need for orthogonal spoiler gradients is prequences to suppress the unwanted echoes by using phase sented, and the number of p/2 and p pulses is kept at a minicycles according to the correct coherence-transfer pathway mum. Experimental verification for the removal of unwanted (3, and/or orthogonal spoiler gradients (5, 6). echoes using the proposed PFGSTE sequence is provided, and preliminary diffusion measurements for ethane in a saturated For diffusion probes without the facility of orthogonal H-ZSM5 zeolite are presented. ᭧ 1997 Academic Press spoiler gradients, we have found, as did Latour et al. (5), that a four-step phase cycle as proposed by Fauth et al. (3) does not suppress the unwanted echoes to a desired degree.