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.