Kinetic theory of resonance and relaxation in spin systems I

The dynamics of the paramagnetic spin (S=12) system, treated as an open system interacting with an alternating magnetic field and a lattice (phonons), is considered. Starting with the generalized kinetic equations, the non-Markovian equations describing the Zeeman, the dipole interaction and the resonant phonon subsystems are obtained with accuracy to terms of the second order in a weak perturbation. The passage from a set of integro-differential equations (so called equations with memory) to equations in the Markovian limit is studied.