Multiple-quantum relaxation in the magic-angle-spinning NMR of 13C spin pairs.
We determine the decay rate constants of zero-, double- and single-quantum coherence for 13C spin pairs in magic-angle-spinning solid-state NMR. The double-quantum coherence is excited by a C7 pulse sequence and converted into zero-quantum coherence by a frequency-selective pair of pi/2 pulses. The zero-quantum coherence is reconverted into observable magnetization by a second pair of pi/2 pulses followed by a second C7 sequence. In a magnetically dilute system where the 13C-13C distance is 0.296 nm, the relaxation rate constants are consistent with a model of uncorrelated random fields at the two labeled 13C sites. In a fully-labelled system with a short 13C-13C distance of 0.153 nm, the measured rate constants are inconsistent with the uncorrelated random field model.
Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, Sweden.
T
T
Karlsson
A
A
Brinkmann
P J
PJ
Verdegem
J
J
Lugtenburg
M H
MH
Levitt
D002247:Carbon Isotopes; D005998:Glycine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008433:Mathematics; D015394:Molecular Structure; D011789:Quantum Theory; D012172:Retinaldehyde / Q000737:chemistry*; D013057:Spectrum Analysis; D019097:Spin Trapping
D002247:Carbon Isotopes; D012172:Retinaldehyde; D005998:Glycine