On the range of validity of Wannier's threshold law for inner-shell ionization by electron impact: Ne 1s

We have measured the relative cross section sigma rel (1s) of Ne is ionization by electron impact in the range of excess energy E 1 =5-430 eV via the intensity of KL 2.3 L 2.3 1 D 2 Auger electrons. The Auger line intensities were obtained by using calculated PCI disturbed lineshapes for the decomposition procedure. For the range of E 1 =10-50 eV the experimental cross section could be fitted by a power law sigma rel (1s) approximately E 11 mu mu with mu =1.08(6). This value is smaller than the Wannier exponent mu =1.127. A possible reason for such a deviation is discussed.