Cross sections of excitation of singlet $F$-series of barium atom by electron impact

The excitation of singlet $F$-levels of barium atom by electron impact is experimentally studied. Manifestations of strong perturbations in the $6s5d^1D_2-6snf^1F_3^\circ$ spectral series are observed. The dependence of the excitation cross sections on the principal quantum number of the upper level in the $6s5d^1D_2-5dnp^1F_3^\circ$ spectral series follows the power law in the range $n=6-8$. The obtained results are compared with those of the previous experiment.