Near-threshold electron-impact doubly differential cross sections for the ionization of argon and krypton

Abstract

We present normalized doubly differential cross sections (DDCS's) for the near-threshold, electron-impact single ionization of argon and krypton, similar to those taken earlier for Ne and Xe [Yates et al., J. Phys. B 42, 095206 (2009)]. The Ar measurements were taken at incident energies of 17, 18, 20, and 30 eV while the Kr measurements were taken at 15, 16, 17.5, and 20 eV. The DDCS scattering angles range from 15${}^{\ifmmode^\circ\else\textdegree\fi{}}$ to 120${}^{\ifmmode^\circ\else\textdegree\fi{}}$. The differential data are initially normalized to available experimental cross sections for excitation of the ground ${\mathit{np}}^{6}$ to the ${\mathit{np}}^{5}(n+1)s$ excited states of the noble gas and, after integration, to well-established experimental total ionization cross sections of Rapp and Englander-Golden [J. Chem. Phys. 43, 1464 (1965)].