Excitation Potentials and Shell Corrections for the ElementsZ2=20toZ2=30

Abstract

Excitation potentials and shell corrections for the elements $Z_2=20\mathrm{}$ to $Z_2=30\mathrm{}$ are evaluated from experimental stopping-power data for 5-12-MeV protons and deuterons. Use is made of Walske's $K$- and $L$-shell corrections and shell corrections calculated by Bonderup on the basis of the Thomas-Fermi model. It is suggested that Cu be used rather than Al as a standard for stopping-power measurements. $I_{\mathrm{Cu}}$ is deduced to be 320.8±3.8 eV. Relative stopping-power measurements by Bakker and Segrè, by Teasdale, by Burkig et al., and by Nakano et al. are normalized to Cu, and mean excitation potentials are found by means of Bonderup's shell corrections. With only a few exceptions, they agree with the $I$ values obtained from our measurements. Within the $Z_2$ interval treated here, it is found that $\frac{I}{Z_2}$ increases with increasing $Z_2$, contrary to the general trend through the periodic system of elements.