The presence of long-lived spin states in organic solids with rapid molecular motions

Abstract

For organic solids with sufficiently mobile molecular segments, the application of a long and weak pulse ( γB 1/2π∼100 Hz) can yield inverted sharp peaks with linewidths of ∼100 Hz in the 1H NMR spectra, and the use of multi-frequency weak pulses can excite multiple inverted sharp peaks. For these compounds, the normal 1H free induction decay (FID) of a static sample contains a slowly decaying part, which can be detected by acquisition delay up to about 2 ms. The presence of highly mobile molecular segments can also be identified by using a “dipolar filter.”