  Redfield master equation was applied to study the dynamics of an ensemble of
interacting pair of unlike spins at room temperature. This spin quantum system
is a workbench quantum model to analyze the relaxation dynamics of a
heteronuclear two-level spin system interacting by a pure dipole-dipole
coupling. Expressions for the density matrix elements and their relaxation rate
constants of each coherence order were computed. In addition, the solutions
were evaluated considering three initial quantum states, and the theoretical
predictions, such as multi-exponential evolutions and enhancement, are
behaviors that the solutions preserve and agree with previous studies performed
for magnetization time evolutions. Moreover, the solutions computed to predict
the dynamics of the longitudinal magnetization avoid the disagreement reported
by I. Solomon.
