DOUBLE PHOTOIONIZATION OF ARGON INTO THE 3S3P(5)(1)P- AND (3)P-STATES

Double photoionization of argon was studied by photon induced fluoresc ence spectroscopy (PIFS). Cross sections for the double photoionizatio n into the 3s3p5 1p, 3p States of Ar++ are presented for exciting phot on energies between threshold and 120 eV. In the threshold range the e nergy dependencies of these cross sections were determined for the fir st time. Singlet and triplet states are populated with comparable prob abilities at equal excess energies, in contrast to predictions of the extended Wannier theory. At hnu = 100 eV the spin-orbit splitting of t he 3s3p5 3P state was resolved, and a cross section for the production of Ar++ 3s(0)3p6 S-1(0) was determined for, the first time.