Delta-kicked spin Floquet operator

For an instantaneous rotation about $x$ followed by free precession about $z$, the just-before-kick one-period operator is $U=e^{-i\Omega T{S}^z}{e}^{-i\Phi S^x}$. Sampling just after kicks reverses the displayed order. The spin generators are dimensionless and the pulse area $\Phi$ is an angle.