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We present an X-ray and multiwavelength study of 33 weak emission-linequasars (WLQs) and 18 quasars that are analogs of the extreme WLQ, PHL 1811, atz ~ 0.5-2.9. New Chandra 1.5-9.5 ks exploratory observations were obtained for32 objects while the others have archival X-ray observations. Significantfractions of these luminous type 1 quasars are distinctly X-ray weak comparedto typical quasars, including 16 (48%) of the WLQs and 17 (94%) of the PHL 1811analogs with average X-ray weakness factors of 17 and 39, respectively. Wemeasure a relatively hard ($\Gamma=1.16_{-0.32}^{+0.37}$) effective power-lawphoton index for a stack of the X-ray weak subsample, suggesting X-rayabsorption, and spectral analysis of one PHL 1811 analog, J1521+5202, alsoindicates significant intrinsic X-ray absorption. We compare composite SDSSspectra for the X-ray weak and X-ray normal populations and find severaloptical-UV tracers of X-ray weakness; e.g., Fe II rest-frame equivalent widthand relative color. We describe how orientation effects under our previouslyproposed "shielding-gas" scenario can likely unify the X-ray weak and X-raynormal populations. We suggest that the shielding gas may naturally beunderstood as a geometrically thick inner accretion disk that shields the broadline region from the ionizing continuum. If WLQs and PHL 1811 analogs have veryhigh Eddington ratios, the inner disk could be significantly puffed up (e.g., aslim disk). Shielding of the broad emission-line region by a geometricallythick disk may have a significant role in setting the broad distributions of CIV rest-frame equivalent width and blueshift for quasars more generally.

X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk?