REDOR Dephasing by Multiple Spins in the Presence of Molecular Motion

✍ Scribed by Jon M. Goetz; Jacob Schaefer

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 202 KB
• Volume: 127
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1997.1198

✦ Synopsis

Closed-form, numerical algorithms are presented for calculating REDOR dephasing for three general cases: (i) collections of isolated I-S spin pairs; (ii) many S spins coupled to an I spin; and (iii) an I-S spin pair in relative motion. For the case when more than one S spin is dipolar coupled to an I spin, the calculation assumes that the S-S homonuclear interaction does not affect REDOR dephasing. Full numerical simulations show that this assumption is true if the S-spin lineshapes are inhomogeneously broadened, the S-spin chemical shifts are far from rotational resonance, and a version of REDOR is used which minimizes the number of S-spin pi pulses. For the rapidly rotating -CF3 group of poly(trifluoroethyl methacrylate), the formalisms of (ii) and (iii) are combined to calculate the dephasing. The experimentally measured dephasing matches theory when the wiggling motion of the -OCH2CF3 moiety of the polymer is taken into account.