Absorption Structure Near theLII,IIIEdge of Argon Gas

We have studied the absorption spectrum of argon in the 50-Å region. The discrete structure observed near the $L_{\mathrm{II},\mathrm{III}}$ edge is attributed to the excitations of a $2p$ electron to the high-lying Rydberg states which converge to the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}\left(L_{\mathrm{III}}\right)$ and ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}\left(L_{\mathrm{II}}\right)$ states of the argon ion. The energy values of the $L_{\mathrm{II}}$ and $L_{\mathrm{III}}$ levels of the argon atom are found to be 250.55 ± 0.05 and 248.52 ± 0.05 eV, respectively.