Theorie der Multipolrelaxation

The multipole resonance and relaxation is discussed starting with a general consideration of the quantum mechanical dynamics of spinsystems with arbitrary spinI. The irreversible entropy production as a function of the multipolarisations is calculated from the density operator, expanded in terms of a complete set of orthonormal multipole operators. By use of the methods of thermodynamics of irreversible processes one obtains relaxation equations, which are a generalization of the Bloch equations of pure magnetic dipole relaxation. They connect the time derivatives of the multipolarisations with affinities, which are defined by the expansion of the logarithmus of the density operator; for small multipolarisations the affinities are equal to the multipolarisations themselves. Relations for the relaxation matrix are discussed, especially a derivation is given for reciprocal relations between the relaxation coefficients. In the special case of spinI=1 the equations of quadrupole relaxation are studied for axial symmetry.