Photoelectron spectra and zero-volt electron scans were measured following synchrotron-radiation excitation of argon, to elucidate the photon energy range between threshold and the Cooper-minimum region of the Ar 3s photoline. A number of the ‘‘correlation satellite’’ lines show a dramatic increase of fractional intensity, yielding a total of about forty observed photolines at threshold. This effect is interpreted as arising from strong interchannel coupling near threshold, yielding high–angular-momentum ionic states otherwise inaccessible. The distinction between ‘‘intrinsic’’ correlation effects due to discrete states and ‘‘dynamic’’ correlations arising through the photoemission process is emphasized.

• Received 8 September 1987

DOI:https://doi.org/10.1103/PhysRevLett.60.1490