Express the Hamiltonian (4.57) for the ammonia molecule in the ∣I⟩-∣II⟩ basis to obtain (4.61). Assume the electric field E=E0cosωt. Compare this Hamiltonian with that for a spin-21 particle in a time-dependent magnetic field that appears in (4.38) and deduce the form for the probability of finding the molecule in state ∣I⟩ at time t if it is initially placed in the state ∣II⟩; that is, what is the analogue of Rabi's formula (4.45) for the ammonia molecule?