Abstract

We develop a theory of a new effect, whereby x-ray radiation with narrow spectral lines is generated by an electron beam passing through a multilayer solid-state structure using a method proposed earlier by Kaplan and Datta. These lines are attributed to the extremely narrow resonances of dielectric constants of materials in the vicinity of the atomic absorption edges. The available data for atomic scattering factor f for all elements in the periodic table show that only K, L, and M absorption edges have sharp resonances and, therefore, are suitable for the effect discussed. The power of the transition radiation is proportional to |Δϵ(λ)|², where Δϵ is the difference between dielectric constants ϵ of two materials forming a multilayer structure. Conventionally, ϵ is represented as ϵ = 1 − f₁r_eλ²N_A/π, where r_e = e²/mc² is a classical electron radius, N_A is the atomic density of material, and f₁ is a real part of the atomic scattering factor f. We have found that for most of the atomic shells and elements, the factor f₁ at the absorption edge can be written as f₁ = Z− A_S + B_S[f_S(ω/ω_S) − 1], where Z is the atomic number, S labels the type of shell, and ω_S is the lowest transition frequency for the particular shell S.

© 1987 Optical Society of America