Secondary electron spectra for ionization of water by high energy electrons

Semiempirical models based on Bethe's theory of energy loss by fast charged particles have proved quite useful in extending the data base of differential ionization cross sections. Implementation of this theory requires evaluation of coefficients in Bethe's asymptotic expansion of the first Born approximation. The authors developed a semiempirical method based on photoabsorption and proton impact ionization data to evaluate coefficients of the first two term in Bethe's expansion. In this paper, the authors use coefficients deduced from photoabsorption data and single differential cross sections for ionization by 1 MeV protons to predict the spectrum of secondary electrons ejected from water vapor by high velocity electrons. Results are compared with the available experimental data