Electron Excitation out of the Metastable Levels of Ar into Levels of the $3p^55p$

We have measured electron-impact excitation cross sections out of the two metastable levels of the $3p^54s$ configuration into the levels of the $3p^55p$ configuration of Ar by observing fluorescence from the decay of these levels (390-470~nm). Metastable atoms are produced in a hollow cathode discharge. After exiting the discharge, the atoms are excited by a variable energy electron beam and the resulting fluorescence from the decay of excited levels is detected by a PMT. To determine cross sections out of each metastable level ($^3P_0$ and $^3P_2$) separately, a Ti:Sapphire laser (pumped by an Ar$^+$ laser) is used to depopulate the target atoms in the $J=2$ metastable level. We find that the cross sections have peak magnitudes between $10^{-17}$ and $10^{-16}$~cm$^2$. These cross sections are one to two orders of magnitude smaller than the corresponding metastable excitation cross sections into $3p^54p$ levels\footnote{G. A. Piech \emph{et al}, Phys. Rev. Lett. \textbf{81}, 309 (1998).}, but are still two orders of magnitude larger than the $3p^55p$ excitation cross sections from the ground state.\footnote{T.~Weber \emph{et al}, Phys. Rev. A \textbf{68}, 032719 (2003).}