Bremsstrahlung emission of a fast charged particle scattered by a Lenz-Jensen atom with a polarized atomic core

We analyze the contribution of the polarization channel to the bremsstrahlu ng emission of a fast charged particle scattered by a multielectron atom wi th the use of the Lenz-Jensen model for the electron density of the target. Within the framework of this approach, we derive a universal expression fo r the complex dynamic polarizability of an atom, which determines the cross section of polarization bremsstrahlung emission in the Born-Bethe approxim ation. Applying this dependence to the calculation of the polarizability of a krypton atom, we have found that the employed approximation leads to smo othing when reproducing the results of consistent quantum-mechanical calcul ation. Based on the calculation of the R factor, defined as the ratio of sp ectral bremsstrahlung cross sections corresponding to the polarization and static channels, we have shown that polarization effects play an especially important role for frequencies on the order of the nuclear charge (in atom ic units). The contribution of the polarization channel increases logarithm ically with the growth in the energy of an incident particle. A simple anal ytic expression for polarization bremsstrahlung losses within a given energ y range is derived. Using the generalized polarizability of a Lenz-Jensen a tom and its electric potential, we have achieved a reasonable accuracy of t he Born-Bethe approximation within the entire spectral range where the pola rization channel plays a significant role.