Excitation of then=4Level ofHe+by Electron Impact on He

The simultaneous ionization and excitation of helium to the $n=4\mathrm{}$ level of ${\mathrm{He}}^{+}$ by 200-eV electron impact on helium has been studied by time-resolved spectroscopy of the $\lambda =4686\mathrm{}$-Å ($n=4\mathrm{}\to 3$) line of ${\mathrm{He}}^{+}$. The study revealed that the excitation process is complex. It appears that only about 70% of the excitation of the $\lambda =4686\mathrm{}$-Å line can be accounted for by direct simultaneous ionization and excitation of the helium atom to the $n=4\mathrm{}$ level of ${\mathrm{He}}^{+}$ under single electron-atom collision conditions.