Absolute Cross Sections for Excitation of Neon by Impact of 20-180-keV ${\mathrm{H}}^{+}$, ${\mathrm{H}}_2^{+}$, and ${\mathrm{He}}^{+}$

The technique of heavy-ion energy-loss spectrometry has been used to measure excitation cross sections for the $\left(2\mathrm{}{p}^5\right)3s$ and $\left(2\mathrm{}{p}^5\right)3p$ electronic configurations of neon by impact of heavy ions upon ground-state neon. The incident particles used were ${\mathrm{H}}^{+}$, ${\mathrm{H}}_2^{+}$, and ${\mathrm{He}}^{+}$ at impact energies from 20 to 180 keV. The results are compared with previous optical measurements of the emission cross sections of lines from these levels as excited by ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ impact. Agreement is not good, neither in shape nor in absolute magnitude, for excitation of the $\left(2\mathrm{}{p}^5\right)3s$ configuration. However, agreement is surprisingly good for excitation of the $\left(2\mathrm{}{p}^5\right)3p$ configuration. A curve-fitting technique has been applied to extract relative singlet-triplet cross sections for levels within the $\left(2\mathrm{}{p}^5\right)3s$ configuration. Almost no triplet excitation is observed for ${\mathrm{H}}^{+}$ and ${\mathrm{H}}_2^{+}$ impact. Significant triplet excitation is observed only for ${\mathrm{He}}^{+}$ impact.