Some Causes of Resonant Frequency Shifts in Atomic Beam Machines. I. Shifts Due to Other Frequencies of Excitation

The quantum theory of an atomic beam machine is set up in matrix form. A new method is then used to derive the Bloch-Siegert shift in the resonance. The results are extended to the case of Ramsey-type excitation. Finally the Bloch-Siegert shift is computed for the present atomic beam frequency standards and found to be well below the accuracy of measurement.