We have discussed the transition rates for RM and SE. In the case of CW microwave irradiation, where relaxation has to be considered, the static solution for the Liouville-von Neumann equation balanced by the relaxation is calculated instead of the instantaneous evolution with the Hamiltonian. In this case RM can dominate the field profile as shown by the solid lines in Figures and as well as the dashed line in Figure which is a simulation result using the SpinEvolution software. As this paper focuses on understanding the origin of the RM effect, a more sophisticated approach for treating relaxation together with the careful experimental studies of the RM effect will be presented in a forthcoming paper.