Scaled electron ionization cross sections in the Born approximation for atoms with55≤Z≤102

Using the generalized oscillator-strength formulation of the Born approximation, the author calculated electron ionization cross sections for all significant subshells of every fourth atom with $55\le Z\le 102$, and for Hg. The calculations used approximate Herman-Skillman wave functions and eigenvalues. The cross sections were put in scaled form, depending essentially on ionization energy only. The scaled cross sections were used with experimental energies to calculate the cross sections for Cs, ${\mathrm{Cs}}^{+}$, Ba, ${\mathrm{Ba}}^{+}$, Au, Hg, Tl, ${\mathrm{Tl}}^{+}$, and Pb. The cross sections so calculated were in good agreement with the measurements. Both inner-shell ionization and excitation followed by autoionization were prominent contributors to the cross section. The scaling procedure was used to calculate the electron ionization cross section of the noble-gas metastable levels, and there is excellent agreement with measured valves for Ne and A. The scaling procedure was used to calculate cross sections for the sequential ionization ${\mathrm{Ni}}^{+1\mathrm{}}$-${\mathrm{Ni}}^{+14\mathrm{}}$ and ${\mathrm{Au}}^{+3\mathrm{}}$-${\mathrm{Au}}^{+14\mathrm{}}$, which were compared with corss sections obtained from the semiempirical expression of Lotz. Good agreement was found for the Ni ions, but there was poor agreement for the Au ions. Lotz's expression is a factor of 3 smaller than our scaled cross section for the $4d$, $4f$, and $5d$ subshells. It is suggested that the absence of measurements on these subshells precluded correct parametrization in the semiempirical expression of Lotz.