This paper presents experimental studies of resonant two-photon ionization
of Mg via the 3s(2) S-1(0) --> 3s3p P-1(1) transition using 285.2 nm CW lig
ht. Dimensionless ratios of the cross section for ionization into a continu
um state of S character relative to ionization into a state of D character
are extracted from data obtained in two independent experiments. We obtain
the values 0.102 +/- 0.003 and 0.096 +/- 0.012, respectively, and compare t
hese to current theoretical predictions.