Validity of the Kramers-Henneberger Approximation

A formal analogy between the classical method of averages and the Kramers-Henneberger approximate description of the dynamics of atomic systems in a strong monochromatic field is used to determine the limits of validity of this approximation. A unified approach is used to confirm the well-known fact that the Kramers-Henneberger approximation can be applied in the limit of superatomic frequencies and it is shown that this approximation also holds when this condition is violated, i.e., when the field frequency falls to a certain value ωcut, and in this case it can be applied in the limit of superatomic fields. The results are compared with data of numerical and laboratory experiments and with the conditions for validity of the Kramers-Henneberger approximation obtained earlier. The relationship between the validity of the Kramers-Henneberger approximation and the problem of determining the adiabatic stabilization threshold is discussed.