Back to Boltzmann! Using Boltzmann statistics,we can determine the relative populations of each of the two spin states: N2/N e-AE/KT .AE is very small (relative to optical EMR)for RF EMR AsAE↓，N2/N1>1(so,N2≈N) .BUT:for absorbance,we want N >N2 .If absorption rate decay rate,not much absorbance can occur before N N2(saturation) .When transition is saturated,NO MORE ABSORPTION!3
Spin-lattice relaxation: 自旋－晶格弛豫 Longitudinal relaxation:纵向弛豫
Spin-lattice relaxation: 自旋－晶格弛豫 Longitudinal relaxation:纵向弛豫
Decay (relaxation)Processes Two decay routes(non-radiative): 1.Spin-Lattice Relaxation (T) -also called:longitudinal relaxation -due to interactions between nuclear spin states and magnetic micro environments in the sample -magnetic micro environments must be at the Larmor Freguency of the absorbing nuclei in order to couple -what will affect coupling efficiency?