Direct spectral optimisation of proton–proton homonuclear dipolar decoupling in solid-state NMR

We show how direct spectral optimisation can be used to provide significantly improved resolution for proton NMR spectroscopy in the solid state. We describe the design of new continuous phase modulated schemes for proton–proton homonuclear dipolar decoupling, exploiting an experimental optimisation procedure through observation of carbon-13 lineshapes. The performance of the resulting eDUMBO homonuclear decoupling sequences is demonstrated with a variety of high resolution proton NMR experiments at 500 and 700 MHz, and at different magic angle spinning speeds.