Two Energy States A nucleus is in resonance when it is irradiated with B state radio-frequency photons having energy equal to the energy difference between the spin states. Bo hv=△E Under these conditions,a proton in the alpha-spin state can absorb a photon a state and flip to the beta-spin Copyright2010 Pearson Prentice Hall.Inc state. Chapter 13 Chapter 13 7 Two Energy States • A nucleus is in resonance when it is irradiated with radio-frequency photons having energy equal to the energy difference between the spin states. • Under these conditions, a proton in the alpha-spin state can absorb a photon and flip to the beta-spin state