Candidate type II quasars from the Sloan Digital Sky Survey. I. Selection and optical properties of a sample at 0.3 < Z < 0.83

Type II quasars are the long-sought luminous analogs of type 2 (narrow emission line) Seyfert galaxies, suggested by unification models of active galactic nuclei (AGNs) and postulated to account for an appreciable fraction of the cosmic hard X-ray background. We present a sample of 291 type II AGNs at redshifts 0.3