  The absolute single photoionization cross-section was measured for Cl-like
K$^{2+}$ over the photon energy range from 44.2 - 69.7 eV at a constant energy
resolution of 0.045 eV. The experiments were performed by merging an ion beam
with a beam of synchrotron radiation from an undulator. The ground-state
ionization threshold was measured at 0.004 eV energy resolution to be 45.717
$\pm$ 0.030 eV. The measurements are rich in resonance structure due to
multiple Rydberg series of transitions to autoionizing states. These series are
assigned spectroscopically using the quantum defect method, guided by
pseudo-relativistic Hartree-Fock calculations for the energies and oscillator
strengths of transitions to autoionizing states. The experimental results,
which include significant contributions from K$^{2+}$ ions initially in
metastable states, are in satisfactory agreement with a linear superposition of
semi-relativistic R-matrix calculations of photoionization cross sections from
these initial states.
