Relative Energy Measurements in the K Series of Argon

The relative positions of the principal features of the emission and absorption spectra of argon in its K series have been measured. The energy difference between the K-series Rydberg limit and the peak of Kβ1,3 is compared with the optical ionization potential. Location of the K-series limit via the experimental ionization potential leads to new values for the LII and LIII terms from measurements of Kα₂ and Kα₁. These are in reasonable agreement with Hartree-Fock calculations, and with recent grating measurements from other laboratories and single-crystal measurements newly reported here.