Proton CRAMPS of NH3 + groups: line broadening and molecular dynamics

Abstract
Increased 1H combined rotation and multiple pulse spectroscopy (CRAMPS) linewidths for protons within NH3 + groups in the solid state have been investigated by variable-temperature experiments. Linewidth variation with temperature can be correlated with specific molecular dynamic processes. With L-[15N]-alanine, both the NH3 + and CH3 group reorientations give rise to specific broadening of the respective CRAMPS signals as the temperature is lowered. Such dynamic processes may be more important than 14N-1H quadrupolar-modified dipolar broadening in determining NH3 + proton lineshapes.