Initial Tests of Possible Second-Born-Term Source of Asymmetry in Forward Electron Ejection by Fast Bare Nuclei

The shapes of continuum capture cusps arising from ejection of target electrons by 15-18 a.u. velocity ${\mathrm{Ar}}^{18+}$ nuclei traversing He, Ne, and Ar are investigated. Observed asymmetries are compared to the second-Born-term asymmetry conjecture by Shake-shaft and Spruch, and to the alternative, first-Born-term asymmetry counter-conjecture by Chan and Eichler. Present evidence favors the former conjecture.