Motional Narrowing: Ask an NMR Expert

[Baggio]

Hi,

I'm hoping there are some NMR'ers around to answer this question, I Just want to understand the jist of what motional narrowing is. I'm looking to apply this to a solid state system.

thanks

 

[JeffKoch]

Are you referring to Dicke narrowing? That as I understand it results from velocity-changing collisions (that don't affect the internal state of the radiator) increasing the time it takes for a radiating atom (or nucleus) to move a straight-line distance equal to the wavelength of emission. If the mean free path between such collisions is less than the wavelength, the line is said to be Dicke narrowed. I can't really understand it except through correlation functions and Fourier transforms that yield spectral line profiles. Perhaps that means I don't fully understand it.

 

[charng]

Motional narrowing is a phenomenon observed in nuclear magnetic resonance (NMR) spectroscopy where the spectral lines of a molecule or solid are narrowed due to the motion of the nuclei. This motion can be rotational, translational, or vibrational in nature, and it causes the nuclei to experience a range of magnetic fields rather than a single one. This results in a distribution of resonance frequencies, which can appear as a broad peak in the NMR spectrum. However, as the motion becomes faster and more random, the distribution of resonance frequencies becomes narrower, resulting in a sharper peak in the spectrum. This is known as motional narrowing. It is a useful tool in NMR spectroscopy as it can provide information about the dynamics and structure of molecules and solids. To apply motional narrowing to a solid state system, one would need to carefully control the motion of the nuclei and analyze the resulting NMR spectrum to extract relevant information about the solid's structure and dynamics.