Abstract
A quantum statistical model for the relaxation of two strongly coupled spin 1/2 particles toward thermal equilibrium is formulated microscopically using a master equation. Raman-type dissipation mechanisms are introduced in addition to the usual bilinear coupling between the coupled system and the reservoir. The effects of two different rotating wave approximations to derive the master equation are investigated. Decoherence is considered as a process toward thermal equilibrium for the dissipative system and is studied by observing the phase and energy relaxation.