Electron Shake-Off in Neon and Argon as a Function of Energy of the Impact Electron

Abundances of satellite lines relative to diagram lines in the $K$-Auger spectrum of neon and $L$-Auger spectrum of argon are measured as a function of the energy of impact electrons. The ratios of satellite to diagram lines are found to be independent of the energy except near the threshold for initial ionization, where the ratios decrease sharply. These ratios are taken to be evidence of the extent of initial double-to-single ionization, i.e., the $\mathrm{KL}$ to $K$ ionization in neon and $\mathrm{LM}$-to-$L$ ionization in argon; and the results are discussed in terms of electron shake-off and the sudden approximation.