In the first step we tilt the frame of reference for the electron spin by θ such that tan θ = ω1S/(ω0S -ωm). Thus the ˜z-axis of the tilted rotating frame is aligned along the effective field. Next, we construct the matrix representation of the Hamiltonian using the basis states, , of the 𝑧-component of 𝑆 6 in the tilted rotating frame and the z-component of I in the laboratory frame: