Polarization Bremsstrahlung of Nonrelativistic Charged Particles on Atoms

Ever since Stokes and Sommerfeld [1] explained the “white” x-ray bremsstrahlung spectrum of cathode rays in the anticathode material, bremsstrahlung has been a subject of experimental and theoretical research. The quantum theory of bremsstrahlung was created by Bethe and Heitler [2, 3], Sommerfeld [1], and Sauter [4]. The need for a quantum theory follows from the existence of a maximum frequency for the x rays, ωmax, which is determined by the initial (subscript i) kinetic energy T i of the incident particle and Planck’s constant: $${\omega _{\max }} = {T_i}/\hbar .$$ (4.1) Of course, under certain conditions the quantum theory transforms to the classical theory. This happens if the energy of the bremsstrahlung photon is considerably lower than the energy of the incident particle, ℏω« T if [more precisely, of the fmal (subscript, f) and initial particles]. Then the quantum mechanical transition current can be replaced by the classical particle current and the quantum mechanical formula for the bremsstrahlung intensity becomes the classical formula.