A Dip in Powder Deuterium NMR Lineshapes

An analysis of powder 2H NMR lineshapes based on the Redfield theory reveal an interesting dip at the center of the powder spectra, that is, at the magic angle β = 54.7. This extra feature, which has completely been ignored in the literature, has interesting dynamic implications. From its presence or absence it is possible to tell whether the dominant dynamic process causing relaxation is fast or slow relative to the inverse of the Larmor frequency, 1/ω0. The angle-dependent lineshape function is derived in closed form and the powder spectra are displayed for two typical cases.