ESR

 

Energy-levels are populated due to the Boltzmann-distribution

 

N_h = N_l . exp(-DE/kT)

 

typical N_h < N_l

~ 1,000007

Absorption --> equally populated energy levels --> no ESR-signal

 

Relaxation mechanisms :

 

1.Spin-Matrix Relaxation

2.Spin-Spin Relaxation

term:

Relaxation time = time necessary to re-establish the Boltzmann-distribution to 1/e.

 

ad 1. Transfer to surrounding atoms

 

                      T₁ =  Spin-matrix-relaxation time

                      T₁ =  In fluids shorter than in solids

                      If T₁ long à saturation --> Lines are small and broad

 

ad 2. Exchange of spin with surrounding atoms

 

 --> Change of spin-life time but not of population

 

                      T₂ = Spin-Spin-relaxation time

                      DE . t = k . h     --> short life time = broad lines

                      In solution line width prop. 1/T₂