The energy dependence of the electron mean free path

Experiments providing multi-point data on electron mean free paths vs. energy in pure materials have been reviewed for energies from 150 to 4000 eV. With the assumption that the simple equation lambda = kEsup(m) can approximate the data, one obtains values of m between 0.53 and 0.80. Observations by ESCA of widely spaced photoelectron lines for Mg, Cu, Zn, Ga, Ge and As also lead to the conclusion that the exponent is considerably larger than 0.5, and is more likely in the range 0.65 to 0.75. (author)