Conceptually, relaxation times in NMR depend on the rotational correlation times (τ

_{c}) of molecules in solution. Wikipedia gives equations for the T1 and T2 relaxation times (

http://en.wikipedia.org/wiki/Relaxation_%28NMR%29#Microscopic_mechanism) and as you can see τ

_{c} appears in both equations. τ

_{c} itself depends on temperature, following the relation:

where, η is the viscosity, a is the radius of the molecule, k

_{b} is the Boltzmann constant, and T is absolute temperature.

Since spin-lattice relaxation is caused by stimulated emission, T1 will be smallest (i.e. T1 relaxation will occur fastest) when the rotational fluctuations occur at a rate comparable to the Larmor frequency of the nuclei being manipulated (i.e. when τ

_{c} ~ 1/ω

_{o}). T2 (spin-spin) relaxation times behave more simply as they always decrease with increasing τ

_{c}.

I hope this was a somewhat clear explanation. Let us know if you are still confused.

P.S. in the future, please refrain from posting the same topic in multiple forums. It is against the

**Forum Rules**. Thanks.

[edit: made the equation in LaTeX so it's more clear]