Resonances in low-energy electron cluster bremsstrahlung

The calculations of low-energy bremsstrahlung cross-sections from alkali metal (lithium, sodium and potassium) clusters of “magic” size (in the range from 8 to 196 atoms) are presented. The ordinary (static) part of the bremsstrahlung cross-sections is expressed via the continuum–continuum dipole matrix element in the length form. The polarization of the cluster by an incident electron is included through the polarization correction to the cluster potential. The clusters are described within a spherical jellium model. The density-functional approximation is used to obtain the cluster potential and electronic wave functions. It is shown that low-energy bremsstrahlung cross-sections from metal clusters have the resonance structure. The resonances are connected with the electron capture in quasi-bound states. Inclusion of polarization effects results in the red shift of the resonances. Dependence of the resonance width and intensity on the projectile electron energy is discussed.