87Rb Spin Diffusion in Ferroelectric RbH2PO4Studied by Two Dimensional Exchange NMR

✍ Scribed by P.M. Cereghetti; R. Kind

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 195 KB
• Volume: 138
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1999.1719

✦ Synopsis

We separate the contributions of spectral spin diffusion and chemical exchange in the 2D exchange NMR spectra of 87 Rb in the pseudo-spin glass Rb 1؊x (ND 4 ) x D 2 PO 4 by studying the 87 Rb spin diffusion in the isostructural compound RbH 2 PO 4 at 85K, where the system is frozen in the ferroelectric phase state. The fact that the spin-diffusion time (T SD ) of a particular point in the 2D spectrum depends essentially on its distance from the diagonal, allowed, even for the case of an unresolved 2D spectrum, to determine T SD as a function of the frequency separation ⌬ over two orders of magnitude. In accordance with existing theories, T SD ؊1 (⌬) was found to be of Gaussian shape. However, we found huge discrepancies between the calculated and the experimentally determined second moments. This failure of the theory is not understood at present.